doc: information on floating patches in point releases

[sxa]

Latest example was 22.0.1.1+1 based off 22.0.1+8 where we floated a patch for s390x.

We should document the expected process and ensure it is possible to follow it. Ensure impliations on installers, containers etc. are understood.

Please describe what you want to be able to do that isn't documented, and/or what you'd like to see in the documentation.