[flyingcircus3]

In my experience, ESP8266 development doesn't rely very much on the datasheet. Thats because there is a large community around one or two chips, and therefore a single driver implementation is good enough for everybody to write high level code on top of. There's little to no register interaction, and no need to look up how the peripherals work. There's no ARM Cortex I can think of that has this development style.