This is the 2nd RFC version of a virtio SPI Linux driver which is intended to be compliant with the proposed virtio SPI draft specification V10. The 1st RFC version sent out publicly was compliant to the virtio draft specification V4. Changes between 1st and 2nd virtio SPI driver RFC: - Update to be compliant to virtio SPI draft specification V10. - Incorporated review comments gotten from the community. A proposal for a performance enhancement having more than only one SPI message in flight had to be kept out. The more complicated code would have caused an unacceptable project risk now. The virtio SPI driver was smoke tested on qemu using OpenSynergy's proprietary virtio SPI device doing a SPI backend simulation on top of next-20240103 and an adapted version on Linux 6.1 with target hardware providing a physical SPI backend device.