This is why forks made for specific devices are seldom updated for more than a few months (or a couple of years if you're very lucky).
I feel like this problem should have a technical solution.
maybe a VCS good enough that this isn't as big an issue? (along the lines of pijul?) or
maybe something from formal verification methods to better enforce or more clearly explain why some drivers cannot be accepted. then again, I don't think the computer science is quite there yet
If your code is out-of-tree, every time someone changes an API that break your build, it's your responsibility to update your for and fix it.
If your code is mainline, the people who change API and break the compilation are on the hook to fix it.
Either the change is accepted upstream meaning that everyone else making changes to the mainline needs to keep it working, or it isn't and they don't.