They tell you the names of many registers. What more do you want?
(I really miss the old days when you got a document that explained everything about your processor. I have an ARM port of an experimental OS waiting for a new board with a complete data sheet. It's been a year so far.)
try reading the SoC spec for the A20. If you can find it.
Googling "AllWinner A20 datasheet" brings in good results.
"Broadcom BCM2836 datasheet" doesn't. All you get is part of the GPIO registers, and absolutely NO electrical specifications. (Part of me really wants someone working there to "take one for the community" and leak the full datasheet. Ironically, that's how the AllWinner docs were originally released.)
(I really miss the old days when you got a document that explained everything about your processor. I have an ARM port of an experimental OS waiting for a new board with a complete data sheet. It's been a year so far.)