| The Problem, as I understand it from my paleolithic point of view, is
| that there is, i.e., no /dev/com0, no /dev/puc0, etc. to determine
| precisely where you're attaching.

No, the puc0 is a multifunction device that has ns16550 controllers
embedded in it.  The problem is when you have different types of serial
controllers.  For example:

com0	at pci dev ? function ?
sab0	at pci dev ? function ?
zs0	at sbus slot ?

Where both of those are mutually exclusive and have the same physical
location in the machine.  Since they have different major numbers you
cannot create a device node that will work for either of those devices.

You really want:

tty0	at com0
tty0	at zs0

Then you can create a single device node that will work for both of those
controllers, regardless of what hardware really is at that location.

| I can imagine that it would be quite frustrating to have to divine which
| port you were on (though plugging in and typing 'tty' once you got to
| single-user mode wouldn't be too difficult  :/  ).

The console is not a big issue since the console device is always 
attached to /dev/console regargless of what device it is.  I want
to do the same for other serial ports.

Eduardo