WIP: Initial docker support

[SrMouraSilva]

To do:

• Audio interface
• Audio plugins
• mod-host?

[MaxPayne86]

@SrMouraSilva docker does not execute on preempt-rt patched kernels. Real-time patch is suggested by mod developers to provide acceptable performances.

[falkTX]

RT patch is kinda pointless on more recent kernels, most of the things for realtime are already on mainline.
So nowadays it is more of a recommendation rather than a requirement, specially if one enables threadirqs boot arg.

[MaxPayne86]

@SrMouraSilva @falkTX please checkout https://hub.docker.com/repository/docker/aidadsp/mod-ui

[MaxPayne86]

I have made extensive tests in the past days by using a 5.10 kernel with CONFIG_IRQ_FORCED_THREADING=y CONFIG_PREEMPT=y as well as starting it with threadirqs boot arg on a Cortex-A53 soc. On userspace I've then configured i2s dma interrupt and jackd priorities with chrt. My conclusion is that Preempt-RT is not a recommendation, is it still required. Everything else works as expected.