Whatever I found so far about different chips, I gathered here. Maybe there's something in it that will help you. I'm happy to work together once I get to the 'software phase' that you're already in, even though I have slightly different chips.
If you find more documentation on any of the chips, feel free to add links to the above topic!
Regarding firmware; nobody is getting access to the code, however I have not yet tried downloading Bitmain firmware updates and throwing them into a disassembler. I have no idea whether they have symbols or not; if not, they will be a bit more tricky to reverse-engineer.