Something that talks about high level structural changes between versions?
I'm not interested in HW platform support changes and details as those are covered in the release notes.
I want something that would help someone porting from version to version to understand what kinds of architectural changes were made and some hints about the kind of things that need to be changed to port from each version to the next version. I can then cumulatively observe those to see what is easy to port to what newer version and where it gets more challenging because of larger architectural changes.
Something short and sweet that gives a few details and high level overview of what architectural changes were made from version to version without the clutter of what HW platform changes were made.
Essentially the release notes should be partitioned into separate sections for "architecture" and "HW platform / chip" changes - with more detail in the "HW platform" section and more big picture / makefile / port-related info in the "architecture" area.