Use Google or Github
Broaden your search, find something close, and port it to a specific model/family of STM32, or SPI equivalent from another MCU family.
Failing that, you or one of your software engineers, will need to read the manuals and code a solution.
https://community.st.com/s/question/0D53W00001aIVhpSAG/using-stm32f407-and-mcp23s17-the-extend-of-ports
