That's only an issue if you're building a general purpose OS that tries to target every ARM board out there. If you're just making a hobby OS on a simple device

That's only an issue if you're building a general purpose OS that tries to target every ARM board out there. If you're just making a hobby OS on a simple device, then you don't really need to worry about it. In the x86 world it would be analogous to saying that you don't need to worry about writing an ACPI engine into your hobby OS.