Ethernet

Ethernet card:
RJ-45 <-> PHY <-> MAC <-> DMA(?) <-> ... <-> software
         (dsp)  (chksum) (middle man between sw and mac)

Ethernet:
Clock: manages time of sending packets (0s, 1s)
Data: normal serial line, like most other serial based things.
MDIO/MII/GMII/etc:
used for speed neg. (is it 10? 100? 1000?) and other things that are not in data ("metadata")