I'm aware you were talking about PCI serial ports, my point is the driver and framework is the same.. the pccom/com(4) frameworks are used regardless of the attach point, so either com at isa? or com at puc? it doesn't matter.
If you look at pccom/com(4) you'll notice at the top that the first 4 numbers [0-3] are reserved for serial ports on the mainboard.. so counting starts at 4, the numbering is 1/1 with the device nodes.. so /dev/{tty,cua}04 would be pccom4/com4.
(
An architecture can only use either the com(4) framework or the pccom(4) framework, not both.)
That's my rant for the day..