Merge pull request #37379 from Kartik494/besteffortpods

Document special case of ResourceQuota for cpu and memory

Author: k8s-ci-robot

content/en/docs/concepts/policy/resource-quotas.md

@@ -39,6 +39,18 @@ Resource quotas work like this:
   See the [walkthrough](/docs/tasks/administer-cluster/manage-resources/quota-memory-cpu-namespace/)
   for an example of how to avoid this problem.
 
+{{< note >}}
+- For `cpu` and `memory` resources, ResourceQuotas enforce that **every**
+(new) pod in that namespace sets a limit for that resource.
+If you enforce a resource quota in a namespace for either `cpu` or `memory`,
+you, and other clients, **must** specify either `requests` or `limits` for that resource,
+for every new Pod you submit. If you don't, the control plane may reject admission
+for that Pod.
+- For other resources: ResourceQuota works and will ignore pods in the namespace without setting a limit or request for that resource. It means that you can create a new pod without limit/request ephemeral storage if the resource quota limits the ephemeral storage of this namespace.
+You can use a [LimitRange](/docs/concepts/policy/limit-range/) to automatically set
+a default request for these resources.
+{{< /note >}}
+
 The name of a ResourceQuota object must be a valid
 [DNS subdomain name](/docs/concepts/overview/working-with-objects/names#dns-subdomain-names).