Hi,

search northernlight.com for "RTL8139C" AND "Linux" will result in 
about 40 URLs.

The realtek homepage says a Lunux and Unix and FreeBSD driver 
is available.

"http://www.openblt.org/dcdev/netboot/" has a "rtl8139c.c" and 
"rtl8139c.h" file that may be interesting.


HTH

mike