This is pretty quick and easy. Wherever possible, try to use naming schemes that are independent of roles, controller or peripheral.
CONTROLLER PERIPHERAL
SDO ----------> COPI ----------> SDI
SDI ----------> CIPO ----------> SDO
This can include:
- SPI
- UART
- extend this.
The first prototype of BART had a signal mix-up. Lucky that nRF can map all pins to all roles.