doc: note that it's possible to use an older cluster with newer device plugins

Signed-off-by: Tuomas Katila <[email protected]>

Author: tkatila

README.md

@@ -280,8 +280,9 @@ matching Kubernetes versions are listed below:
 | release-0.15      | Kubernetes 1.15 branch v1.15.x | unsupported |
 | release-0.11      | Kubernetes 1.11 branch v1.11.x | unsupported |
 
-[Go environment]: https://golang.org/doc/install
-[Kubernetes cluster]: https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm/
+*Note:* Device plugins leverage the Kubernetes v1 API. The API itself is GA (generally available) and doesn't change between Kubernetes versions. One doesn't necessarily need use the latest Kubernetes cluster with the latest device plugin version. Using a newer device plugins release should work without issues on an older Kubernetes cluster. One possible exception to this are the device plugins CRDs that can vary between versions.
+
+[Go environment](https://golang.org/doc/install) | [Kubernetes cluster setup](https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm/)
 
 ### Release procedures