DUE schematic doubt Altium
That is almost certainly Ethernet that appears to go to a connector of some description. This is the RMII or RGMII port (That is clear from the two data bits in each direction rather than 4)

The signal naming convention seems to be:

E (Ethernet)

Signal direction for signals that have specific direction: TX (Transmit), RX (Receive)

Signal name 

Port ID This is all on ethernet port A

So ETXD0A is Ethernet, Transmit, D0 (data bit zero), port A.