#1 Update: Recent Rapsberry Pi (downstream) kernel dt-overlays now exposes a config option "krnbt" that negates the need for all this.
Relevant PRs: raspberrypi/linux#3682
[Pi 3B (Non-Plus) / Pi Zero W ONLY]
As of kernel package, linux-raspberrypi-4.14.59-1
, support for notifying the kernel of the