I think I've found what I needed in the header of ESP8266Gateway.ino:
* See http://www.mysensors.org/build/ethernet_gateway for wiring instructions.
* The ESP8266 however requires different wiring:
* nRF24L01+ ESP8266
* VCC VCC
* CE GPIO4
* CSN/CS GPIO15
* SCK GPIO14
* MISO GPIO12
* MOSI GPIO13
