[OSDOCS-19638] Add channels topics to upgrading section in OSD docs

modules/create-wif-cluster-cli.adoc

@@ -55,7 +55,7 @@ $ ocm create cluster <cluster_name> \
 --min-replicas=3 \
 --max-replicas=6 \
 --secure-boot-for-shielded-vms=true
---channel-group <channel_group_name>
+--channel <channel_name>
 ----
 +
 where:
@@ -91,7 +91,7 @@ For more information about supported versions for WIF configurations, see "Creat
 
 `--secure-boot-for-shielded-vms=true`:: Enables Secure Boot, which allows the use of Shielded VMs in the {gcp-full}. This parameter is optional.
 
-`--channel-group <channel_group_name>`:: Specifies the name of the channel group you want to assign the cluster to. Channel group options include `stable` and `eus`. Replace `<channel_group_name>` with the desired channel group. This parameter is optional.
+`--channel <channel_name>`:: Specifies the name of the channel you want to assign the cluster to. Channel options include `stable`, `fast`, and `eus`. Replace `<channel_name>` with the desired channel. This parameter is optional.
 
 [IMPORTANT]
 ====

modules/osd-lifecycle-policy.adoc

@@ -8,6 +8,6 @@
 = Life cycle policies and planning
 
 [role="_abstract"]
-To plan an upgrade, review the _{product-title} update life cycle_ guide in the "Additional resources" section. The life cycle page includes release definitions, support and upgrade requirements, installation policy information, and life cycle dates.
+To plan an upgrade, review the _{product-title} update life cycle_ guide in the _Additional resources_ section. The life cycle page includes release definitions, support and upgrade requirements, installation policy information, and life cycle dates.
 
-You can use update channels to decide which Red Hat {OCP} minor version to update your clusters to. {product-title} supports updates only through the `stable` channel. To learn more about OpenShift update channels and releases, see link:https://docs.redhat.com/en/documentation/openshift_container_platform/latest/html/updating_clusters/understanding-openshift-updates-1#understanding-update-channels-releases[Understanding update channels and releases].
+You can use update channels to decide which Red Hat {OCP} minor version to update your clusters to. {product-title} supports updates through the `stable`, `fast`, and `eus` channels. To learn more about OpenShift update channels and releases, see the _Additional resources_ section.

modules/osd-upgrading-channels.adoc

@@ -0,0 +1,37 @@
+:_mod-docs-content-type: CONCEPT
+[id="osd-upgrading-channels_{context}"]
+= Channels in {product-title} clusters
+
+[role="_abstract"]
+You can view the options available for upgrading your cluster by using {product-title} channels. By using channels, you can update with the available patches/z-stream updates in your existing channel, then you can choose to view the update path to a newer Y-stream version by selecting the appropriate channel.
+
+== Channel groups and Channels
+Channel groups in {product-title} are similar to Channels, but there is no specific version with channel groups. When you select a channel group, you can avail of certain updates to your {product-title} cluster. These channel groups typically include:
+
+* Fast: cluster receives the latest updates as soon as they are available.
+* Stable: cluster receives updates after they have been thoroughly tested.
+* Eus: Extended Update Support channel, allowing for extended support for even-numbered versions, for example, 4.16, 4.18, 4.20
+
+Moving from Channel groups to Channels enables you to have more control over your cluster upgrades. Instead of receiving patch/z-stream updates only for a particular channel group, by using Channels you can view the available updates associated with a minor release version, and determine if there is a path available to that minor/Y+1/Y+2 version.
+
+The process for upgrading your cluster is based on the updates that are available for your current version, and what level of release you are interested in, such as z-stream or y-stream updates.
+
+* Patch (z-stream) updates: You do not need to change the channel when performing a patch update within your current minor version.
+* Minor version (y-stream) updates: To upgrade to a new minor release, you must change the channel to the next release channel (for example, switching from `stable-4.20` to `stable-4.21`).
+* Switching channels: You can change your cluster's channel either through the Administration → Cluster Settings page in the web console or by using the CLI command `rosa edit cluster -c <cluster_name_or_id> --channel <channel_name>`.
+
+When you have set the channel and an update is initiated, the Cluster Version Operator (CVO) retrieves the target release image and begins applying the changes to the cluster.
+
+== Path to Y+1 and Y+2 updates
+
+You can upgrade to the available patches/z-stream updates in your existing channel, and then you can choose to view the upgrade path to a newer Y-stream version by selecting the appropriate channel. For example, if you have your cluster at version 4.19.12, you can stay within your current `stable-4.19` channel, and decide to upgrade your cluster when there are updates available, such as 4.19.13, 4.19.14, 4.19.17, 4.19.20 until you have the latest updates for that minor version.
+
+Next, you can switch the channel to `stable-4.20` or `stable-4.21` and check if there is an upgrade path available for those versions. For example, if `stable-4.20` has an upgrade path available, it shows you the z-stream updates for your current version, as well as the updates to the Y+1 version, such as 4.19.14, 4.19.17, 4.19.20, 4.19.23, 4.19.27, 4.20.0. If you had selected `stable-4.21`, the available updates might be 4.19.14, 4.19.17, 4.19.20, 4.19.23, 4.19.27, 4.20.0, 4.20.3, 4.20.4, 4.20.6, 4.20.7, with all the z-stream/patch updates displayed right through to the Y+2 version of 4.21.0.
+
+////
+[NOTE]
+====
+The *Channel groups* option is now deprecated in {product-title}. Channel groups allowed you to upgrade through the available patch/z-stream updates for a particular channel group, such as stabe or eus. 
+There was the possibility of inadvertently upgrading to the next minor version/Y+1 version if it appeared in the available updates.
+====
+////

modules/osd-upgrading-switch-channels.adoc

@@ -0,0 +1,30 @@
+// Module included in the following assemblies:
+//
+// * upgrading/osd-upgrades.adoc
+
+:_mod-docs-content-type: PROCEDURE
+[id="osd-upgrading-switch-channels_{context}"]
+= Switch channels to view available upgrade options
+
+[role="_abstract"]
+You can switch the channel options on a {product-title} cluster to access the preferred upgrade options within a minor version (Y-stream), or to upgrade to the subsequent minor versions (Y+1, Y+2). The version number in the channel represents the target minor version for which you want to see upgrade options.
+
+For example, if you're currently on `stable-4.18`, you can switch the channel to `stable-4.19` and view the updates that are available to get from 4.18.z to 4.19.z, providing there is a path from your current cluster version to 4.19.z. This strategy ensures that administrators must explicitly decide to update to the next minor version of {product-title}, and prevents automatic minor version upgrades.
+
+.Procedure
+
+. Log in to {cluster-manager-url}.
+. Select a cluster for which you want to see the upgrade options.
+. Click Administration > Cluster Settings. 
+. In Cluster Settings, click the *Details* tab.
+  * The *Channel* displays the current update channel for the cluster, such as stable-4.17.
+. Next, select the new update channel.
+.. Click the edit channel icon.
+.. On the Input channel dialog, enter the required channel version, for example, stable-4.18.
+.. Click *Save*.
+** The upgrade options for your selected Channel will be displayed in the Available Upgrades list.
++
+[IMPORTANT]
+====
+The Channel group option is being deprecated. If you set a channel group only, {product-title} will default to preserving the current channel's target version. For example, a stable-4.20 cluster moving to the eus channel group will use the eus-4.20 channel by default, if the current cluster version is a member of the eus-4.20 channel.
+====

upgrading/osd-upgrades.adoc

@@ -14,18 +14,23 @@ Red Hat Site Reliability Engineers (SREs) monitor upgrade progress and remedy an
 
 include::modules/osd-lifecycle-policy.adoc[leveloffset=+1]
 
-[role="_additional-resources"]
-.Additional resources
-* xref:../osd_architecture/osd_policy/osd-life-cycle.adoc#osd-life-cycle_life-cycle-overview[{product-title} update life cycle]
-
 include::modules/upgrade.adoc[leveloffset=+1]
 
+include::modules/osd-upgrading-channels.adoc[leveloffset=+1]
+
+include::modules/osd-upgrading-switch-channels.adoc[leveloffset=+1]
+
+include::modules/upgrade-auto.adoc[leveloffset=+1]
+
+include::modules/upgrade-manual.adoc[leveloffset=+1]
+
 [role="_additional-resources"]
 .Additional resources
 
+* xref:../osd_architecture/osd_policy/osd-life-cycle.adoc#osd-life-cycle_life-cycle-overview[{product-title} update life cycle]
+
+ * link:https://docs.redhat.com/en/documentation/openshift_container_platform/latest/html/updating_clusters/understanding-openshift-updates-1#understanding-update-channels-releases[Understanding update channels and releases]
+
 * xref:../osd_cluster_admin/osd-cluster-notifications.adoc#managed-cluster-notification-view-hcc_osd-cluster-notifications[Accessing cluster notifications in {hybrid-console}]
 
 * xref:../osd_gcp_clusters/creating-a-gcp-cluster-with-workload-identity-federation.adoc#wif-configuration-update_osd-creating-a-cluster-on-gcp-with-workload-identity-federation[Updating a WIF configuration]
-
-include::modules/upgrade-auto.adoc[leveloffset=+1]
-include::modules/upgrade-manual.adoc[leveloffset=+1]