Philippe Gerum authored Sep 25, 2018 and Dmitriy Cherkasov committed Nov 21, 2018

Raspberry 3 has two UARTs: uart0 is a full-fledged pl011 used for BT
by default, uart1 is a poor-man's low throughput serial device dubbed
as the "mini-uart". Unfortunately, uart1 is a massive pain, whose
clock rate is based on the CPU clock rate: this makes it quite
unstable as a serial console when a CPU frequency governor is enabled.

When BT is useless, we'd rather switch uart0 from BT to the serial
pins, disabling uart1 in the same move, so that we recover a decent
console device (*) with a stable clocking.

bcm2837-rpi-3-b-nobt.dtb is a fixed up blob doing exactly that.

(*) cmdline should mention console=ttyAMA0,<speed>