https://github.com/raspberrypi/documentation/tree/master/har...
and that of the Allwinner A64 in the far less common "Banana Pi":
https://github.com/OLIMEX/OLINUXINO/tree/master/HARDWARE/A64...
As you can see, the Broadcom documentation is non-existent, with the exception of a tiny document created by a third party.