[TF-M] [RFC] PSA Isolation (level 3) design document

Hi,

We have created one PSA Isolation implementation design document and now call for comments: https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/4730

The overall goal is to cover all isolation levels into this one document, and at current stage we take level 3 as an example.

The image layout and regions are based on the assumption of the existing TF-M code base.

Feel free to put comments, or post under this task: https://developer.trustedfirmware.org/T778

Thanks.

/Ken