I have a couple of device tree source questions, which are less specific than I normally post. Also, if my questions here are outside the scope of CircuitDojo Community, kindly let me know and I will delete my post.
I am exploring RaspberryPi’s RP2040 on a DEV-18288 board, and have managed to get some Zephyr sample apps working there with minor device tree file changes. I see however that the primary SoC device tree description is at this time incomplete: it lacks dts nodes for this MCU’s DMA and SPI controllers. Dts file here:
I’m also looking at the DMA and SPI sections of the RP2040 datasheet as found at https://datasheets.raspberrypi.com/rp2040/rp2040-datasheet.pdf.
Can anyone here offer some insight as to how I go from the control and status register descriptions in RP2040 datasheet section “4.4 SPI”, and express those in the needed device tree key+value pairs? I have found and studied some example SPI nodes from Nordic SoC device tree sources. For example, there are SPI nodes expressed in Zephyr supported board / SoC device tree files “nxp_lpc55S6x_common.dtsi” and “nrf9160_common.dtsi”.
The questions I am asking about how to craft correct key+value pairs go beyond the intro device tree guides I have studied so far. So my general question is, what resource / example / or guide can I look to for help to add specific peripheral support for a newer, not fully dts-supported MCU?