OSSMDOC-720: Add more detail to Gateway API enablement docs

Author: rh-tokeefe

modules/ossm-rn-new-features.adoc

@@ -242,8 +242,22 @@ This release marks the end of support for {SMProductShortName} Control Planes ba
 * Gateway injection is not a supported feature.
 
 === Kubernetes Gateway API
-Kubernetes Gateway API is a technology preview feature that is disabled by default.
+:FeatureName: Kubernetes Gateway API
+include::snippets/technology-preview.adoc[]
 
+Kubernetes Gateway API is a technology preview feature that is disabled by default. If the Kubernetes API deployment controller is disabled, you must manually deploy and link an ingress gateway to the created Gateway object.
+
+If the Kubernetes API deployment controller is enabled, then an ingress gateway automatically deploys when a Gateway object is created.
+
+==== Installing the Gateway API CRDs
+The Gateway API CRDs do not come pre-installed by default on OpenShift clusters. Install the CRDs prior to enabling Gateway API support in the SMCP.
+
+[source,terminal]
+----
+$ kubectl get crd gateways.gateway.networking.k8s.io || { kubectl kustomize "github.com/kubernetes-sigs/gateway-api/config/crd?ref=v0.4.0" | kubectl apply -f -; }
+----
+
+==== Enabling Kubernetes Gateway API
 To enable the feature, set the following environment variables for the `Istiod` container in `ServiceMeshControlPlane`:
 
 [source,yaml]
@@ -261,6 +275,21 @@ spec:
 ----
 Restricting route attachment on Gateway API listeners is possible using the `SameNamespace` or `All` settings. Istio ignores usage of label selectors in `listeners.allowedRoutes.namespaces` and reverts to the default behavior (`SameNamespace`).
 
+==== Manually linking an existing gateway to a Gateway resource
+If the Kubernetes API deployment controller is disabled, you must manually deploy and then link an ingress gateway to the created Gateway resource.
+
+[source,yaml]
+----
+  apiVersion: gateway.networking.k8s.io/v1alpha2
+  kind: Gateway
+  metadata:
+    name: gateway
+  spec:
+    addresses:
+    - value: ingress.istio-gateways.svc.cluster.local
+      type: Hostname
+----
+
 == New features {SMProductName} 2.1.5.2
 
 This release of {SMProductName} addresses Common Vulnerabilities and Exposures (CVEs), contains bug fixes, and is supported on OpenShift Container Platform 4.9 or later.