Erwan Gouriou

@MaureenHelm Would you mind having a look ?

@MaureenHelm Kind reminder

> Nit: maybe these comments should be moved to stm32_dma.h? Well, bindings are where all these are supposed to be documented https://docs.zephyrproject.org/latest/build/dts/api/bindings/dma/st%2Cstm32-dma-v1.html#dtbinding-st-stm32-dma-v1

@teburd Up to you (or you can assign it to me)

Looks like a sane proposal from my user point of view, if I understood everything.