The purpose of the email is to notify about deprecation of sgm775 platform and proposed process for deprecating a platform.

Arm's System Guidance for Mobile(SGM-775) is an old platform and no longer maintained. It is superseded by Total Compute(tc0) platform.

Proposal for deprecating a platform:

1. Keep the code in repository. (at least for 2 release cycles)

2. Don't allow it to be built by default. (introducing PLATFORM_DEPRECATED build macro)

3. Disable CI testing.

4. Create appropriate documentation for deprecated platforms.