What do you mean by documented? Sure we have a general idea of how stuff works, and some implementations can even serve as a reference but almost nothing is doc

What do you mean by documented? Sure we have a general idea of how stuff works, and some implementations can even serve as a reference but almost nothing is documented in an official sense. Your average Chinese SBC is much, much better documented, in the sense that the SOCs are at least officially documented. The Broadcom soc isn't.