[TF-M] TF-M Crypto service design document

Hi all,

I have uploaded the design document for the TF-M Crypto service at the following Gerrit code review in RST format: https://review.trustedfirmware.org/c/trusted-firmware-m/+/1023 It can be possible to render the HTML format of the design document by checking out the patch above and build the docs (in particular, by building the install_userguide target) Comments are welcome, here in this thread or preferably in the Gerrit review for better tracking.

Thanks, Antonio