Using emonESP with SPI Serial port

Looking for info on how to redirect serial input to read from the SPI port on the ESP8266 (Huzzah) in the firmware. I have a lora board (RFM9x) connected on this port rather than the serial UART and it will receive string:value pairs in the same way as from an emonTx.

The device will act as a lora/WiFi relay between several sensors and a MQTT broker.

This would split the debug and input ports. I have had a look at the code and can’t find where serial ports are mapped to hardware. Any pointers appreciated.