[TF-M] Using git submodules for dependencies?

Hi,

I'm currently working on integrating TF-M into Zephyr and getting TF-M working with QEMU. Part of that work is simplifying the setup and build process to generate a TF-M secure library.

Was the idea of git submodules for dependencies considered and rejected? Using sub-modules would reduce the number of setup steps required, and pair external dependency versions with specific TF-M commits/releases.

There may be a valid reason this approach was rejected, but it seems like a sensible option on the surface?

Best regards, Kevin Townsend