RFC: SoC audio framework

[Oleksandr Tymoshenko]

Hi,

For some time I've been working on an audio support for ARM-based SoCs.
I submitted the framework part for review and also on included two drivers
to illustrate the framework usage. It's pretty low-intrusive and
self-contained so I don't expect to break things in a major way but
would appreciate if somebody went through it with a fresh pair of eyes.

Review URL: https://reviews.freebsd.org/D27830

Full branch with more drivers: https://github.com/gonzoua/freebsd-src/tree/projects/socaudio

Thank you

-- 
gonzo