How do I upgrade Cassandra 3.11 to 4.0 running in a home-grown Kubernetes cluster?

Question

I have got a Cassandra cluster running on our self hosted Kubernetes cluster, The StatefulSets are deployed using public Cassandra images and it is currently running with version 3.11.5 , I am planning to upgrade it to 4.0.0 without any downtime, but not quite sure about the procedure. I did searched a lot, but most of the references doesn't speak about upgrading docker based clusters running on Kubernetes, appreciate if someone could share any pointers on this, Thanks!