The kernel is something that moves forwards continuously and relentlessly so the adage "If you stand still, you're actually moving backwards" applies in a big way and because (for good reasons) people became inactive for a while a whole heap of WIP changes got parked for a while. I don't think there's a single series, it's more a case of "a little bit of everything" as the kernel evolved.
Im picking up what you're putting down. As opposed to the windows way of doing things where operating systems are just stacked on top of one another forever. Where your windows 2000 program will still run through 7 shims, and if you dive too many layers deep in the menus you'll end up in a program with an unresizable tiny window from when monitors were 480p, because why would anyone ever need to resize a window 😂.
I was just curious, I know there was an effort or push to overhaul and standardize the requirements for manipulating graphics around kms and drm to help make things less of a wild wild west. Probably pretty helpful in the long run for projects supporting wide range of devices, although painful in the short term. Especially with manufacturers of sbcs that like to play the hype release abandon cycle on repeat.
I was helping Moonlight-qt project who lost thier HDR support because setting 1 property on 1 connector instead of atomically, the kernel just said no after a certain version. I think those changes started around 3.19 but ran parallel and weren't enforced until well into the 6.x versions. I was just curious if the rock chip HDMI was a casualty of that same standardization effort with kernel graphics coming to completion.