WL commands for WCN3620 WiFi chip on DB410c

Hi, I’m new to the Forum and I am working on the Dragonboard 410c. The WiFi chip on the Dragonboard is Qualcomm’s WCN3620. In the “WCN3620 Wireless Connectivity IC Device Specification” document, page 25, it shows that there is a 5 wire WL_ communication port (WL_CMD_SET, SL_CMD_CLK, WL_CMD_DATA[2:0]). Does anyone know what the protocol is for the WL bus?