Ethernet Adapter over SPI Interface

[MoD01]

I want to use the Armory like a LANturtle (to Man-in-the-Middle the traffic between USB Host and Server).

[HOST (victim)] //<--USB -- [USBarmory] //<--SPI-- [EthernetModule] //<-- [EthernetCable] .. Network.. 

For this want to add an ethernet module like the SunFounder ENC28J60 Ethernet LAN Network Module.

Can you assist me with the kernel modifications to get to work SPI / ethernet to work using a second network interface ?

Edit:
Of course I have to enable SPI first : https://github.com/inversepath/usbarmory/wiki/SPI
But how can a network interface be configured for ethernet over SPI ?