@wolf480pl @muvlon They're custom ARM CPUs with different capabilities and often completely different ways to boot them and bring them online. They can't be supported with a common/shared framework in the kernel.

aarch64 is an example of a common ARM CPU standard that can be supported and they'll all support UEFI instead of special binary blobs

I'm not an expert in this area but I've read into it a bunch and talked to devs about it, especially FreeBSD kernel devs. I'm sure others can chime in with more precise details