Unix PC internals docs ?

[Patrick Barron]

I'm looking for documentation on:

  1) Writing dynamically-loadable device drivers under Unix 3.51,
  2) Documentation on the combo board (like, how one would get to
     the serial ports from the kernel).

I'm trying to write a device driver that "takes over" a serial port and
runs network protocols over it.

Does anyone have this sort of documentation, or know where I can get it?

--Pat.