APU1 bricked on stable/14 - solved

I have a few pc-engines APU1 appliances running in headless mode under
Nanobsd. Maintenance is by means of  direct COM port connection.
After a recent update a few weeks back I was not able to connect by COM
port anymore - console output and input went away after booting and
before single- or multi-user mode would start. Even re-flashing the
SDcard with a fresh image did not help.

After some longish trials and errors it turned out that both
- commit 74b9fc7a 'amd64 GENERIC: Switch uart hints from "isa" to
"acpi"' as well as
- commit 4ba4cfaf 'acpi: Narrow workaround for broken interrupt settings
on x86'
broke things for me. Restoring hints and setting
hw.acpi.override_isa_irq_polarity=1 in /boot/loader.conf.local restored
working order.

I agree that APU1 is EOL, however I would have expected an entry to
UPDATING for such a POLA violation.

Note that pc-engines APU2 models are not affected as the BIOS ACPI
tables contain correct UART descriptions.

- Stefan