Hi all,

I'd like to propose to adjust the platform folder structure. Would you please check the details below and share your opinions? Any suggestion or feedback will be very helpful.

In current platform folder structure, all the targets are listed together at the same level under `target` folder.

Platform        |-- ext                 |-- .                 |-- target_xxx.cmake                 |-- .                 |-- target_zzz.cmake                 |-- target                           |-- mps2                           |-- musca_a                           |-- .   A drawback is that, there are many duplicated files in those targets folders. It may become difficult to maintain the target support when targets, platforms, drivers and features continue growing. - A platform may have a series of variants. If each variant target folder has to contain a copy of platform drivers or library, it is difficult to align and maintain the duplicated drivers. - All targets belonging to the same platform contain the duplicated common operation files or configurations, such as HUK, NV counter and platform configurations. A small change has to be applied to multiple identical files.

To solve the duplicated files management issue, I'd propose to insert partner folders under `target` and move the targets under the partner folder. The proposed structure looks like the following:

Platform        |-- ext                 |-- target |                          |-- Partner ABC                          |         |-- *common drivers and files*                          |         |-- target_abc_1                          |         |           |-- target_abc_1.cmake                          |         |-- target_abc_2                          |                          |-- Partner XYZ                          |          |-- *common drivers and files* | |-- target_xyz_1 | | |-- target_xyz_1.cmake | |-- target_xyz_2 |-- ...

The ideas behind the proposal: - It is more close to the platform support structure in popular RTOSs. It can be more convenient for partners to port platform support to TF-M from existing projects. - Common drivers and operations implementations can be gathered into partner/platform specific folder. Thus each partner/platform folder doesn't have to hold a duplicated copy. - It is easier for partners to fully organize and maintain their platform folders with full permission. More layers can be added under a specific partner folder, such as diverse platforms. - Put the target specific cmake config file back into the target folder. It can make the `platform` folder much more clear.

Best regards, Hu Ziji