Any standard serial/parallel/joystick/combo cards. Linux supports 8250, 16450, 16550, and 16550A UART's. Cards that support non-standard IRQ's (IRQ > 9) can be used.
See National Semiconductor's ``Application Note AN-493'' by Martin S.
Michael. Section 5.0 describes in detail the differences between the
NS16550 and NS16550A. Briefly, the NS16550 had bugs in the FIFO
circuits, but the NS16550A (and later) chips fixed those. However, there
were very few NS16550's produced by National, long ago, so these should
be very rare. And many of the ``16550'' parts in actual modern boards are
from the many manufacturers of compatible parts, which may not use the
National ``A'' suffix. Also, some multiport boards will use 16552 or 16554
or various other multiport or multifunction chips from National or other
suppliers (generally in a dense package soldered to the board, not a 40
pin DIP). Mostly, don't worry about it unless you encounter a very old
40 pin DIP National ``NS16550'' (no A) chip loose or in an old board, in
which case treat it as a 16450 (no FIFO) rather than a 16550A. - Zhahai
Stewart <zstewart@hisys.com>