Hi. We at Nordic are running the TF-M regression and PSA architecture tests on our boards, and we get occasional issues with test output because HW flow control is by default disabled in CMSIS. To enable HW flow control in the TF-M we must change the call to the CMSIS UART driver.

I've created a change to allows the platform to set any non-default CMSIS configuration, such as HW flow control: https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/20374

I'd like to ask all platform maintainers to review this change.

This change must add another define to all supported platforms, the change itself should not cause any difference in actual behavior. This can be used for other non-default UART configuration in other platforms as well.

-Joakim Andersson