I am trying to find a way? If I create a new namespace then I want it to create a RBAC rule for that serviceaccount automatically.
I know one way is to create an operator so, that there is an event that is traced by reconciler / api server and it creates the resources based on CRD's. Is there any other way?
I asked a similar question here: Automatically create Kubernetes resources after namespace creation (I didn’t find yours at that time).
I ended up writing a controller that does exactly what you need: https://github.com/blakelead/nsinjector
In short, you deploy a custom resource specifying resources to deploy and patterns for namespace names you want to target.