One of the Pi Engineers helped out with this answer and suggestion.
And the later 'h file and tools used within the
https://elixir.bootlin.com/linux/latest/source/include/linux/spi/spi.h makes this investigation very simple.
Re: #include files for https://www.kernel.org/doc/html/v4.14/driver-api/spi.html Pi5 C/C++ development environment
Quote
Tue Jun 11, 2024 1:21 pm
It's always best to look at the docs appropriate for the kernel you're working with - 4.14 was released in 2017, although it has only just been dropped from the LTS support (Jan 2024).
https://www.kernel.org/doc/html/v6.6/driver-api/spi.html
The easiest way to find things in the kernel tree is to use https://elixir.bootlin.com/
https://elixir.bootlin.com/linux/latest/source/include/linux/spi/spi.h is where the SPI structures are defined. Yes RP1 (and bcm2835 before it) use the standard APIs.