keziaha, thank you for your patience.
The SPI bus is implemented into SoC as an interface for SPI flash storing BIOS and TxT firmware. The SPI Flash, as a device is soldered on a motherboard. Where are you trying to see the device? Are you using some software or are you looking for this device in motherboard specification? We need a bit more clarity on this matter to understand the request better and provide most complete answer.
It is entirely possible that, for security, the BIOS is hiding the SPI bus interface completely. As a general rule, runtime software has no business accessing the SPI bus and especially not the flash component.