SPCR and default serial port

[Herrenschmidt, Benjamin]

Hi !

Today, arm64 allows the serial port specified in ACPI SPCR table to be
selected as a default console, but x86 doesn't (second argument to
acpi_parse_spcr).

I understand while we might have been worried of breaking existing
setups back then but should we re-think this, maybe via a CONFIG option
?

It makes a lot of sense to have firmware tell us which of the
potentially many serial port in a system is our active console, along
with its configuration...

This also shouldn't cause problem on systems that already specify a
console explicitly on the command line.

Any opinion ?

Cheers,
Ben.