Current mdev.conf statement for loading bluetooth firmware on Pi
devices has a number of pitfalls, particularly when it comes to
transmit significant data streams, like for a2dp audio:
- serial port connection baudrate is insufficient
- btattach does not work properly, and hciattach (though depreciated)
remains the only option for now (consistently reported in bluez-alsa
github issues & al.)

As a reference one can refer to how Pi Foundation do setup bluetooth
[1], which reliably works. I tested that script on Alpine (with one
slight edit as /dev/serial is /dev/ttyAMA0), it just works great.

I can see 2 options to fix that for good in Alpine:
1) integrate that patched btuart script in /lib/mdev/ and have
mdev.conf rule link to it

2) create a new pi-bluetooth package that adds a pi-bluetooth service
at boot, which uses same script

Which would be the proposed option?
Thanks for feedback and suggestions


[1]https://github.com/RPi-Distro/pi-bluetooth/blob/master/usr/bin/btuart