Hey folks. Today is the day, when I close the task that I was trying to solve for 3 years, with many many attempts. Finally, together with my friend Claude, we managed to do it.

It is 2.1 configuration with two TAS5805M DACs daisy-chained working on Linux the way it should - Single sound card, two codecs, driven by two kernel module instances, **individually controlled** via Alsa. 

Main DAC driver stereo speakers, with 15-band EQ available. Secondary DAC drives a single subwoofer channel in bridge mode, with frequency adjustable LF filter.  Seriously, I was fighting kernel module and device tree for 3 YEARS to make it work the way it should!

The code and docs are here. Next stop is TAS5825M version of the Louder Raspberry Hat, with dual-DAC variant from the start.