Embedded devices aren't known for security anyway. And the tls library can be written in rust for better memory safety.
If you want a TLS library written in Rust there's already rustls, no need to reinvent the wheel.
Unfortunately it's not entirely clear if rustls can compete in the embedded space where Mbed TLS is most popular?
As a rustls maintainer, we'd love to get feedback about this and/or work with organizations that want to sponsor getting rustls to the point that it could!