Need more information. Are you trying to use a chipset (already supported by linux) with a synchronous serial port? Most ethernet drivers are pci, but I suppose you might be able to adapt them to ssp.
Read (all from linux sourcetree):
Code:
Documentation/driver-model/overview.txt
Documentation/networking/driver.txt
Documentation/networking/netdevices.txt
Documentation/pci.txt
Documentation/spi/spi-summary
ethernet
