mbedtls/ChangeLog.d/support-ecdh-kdf-with-ecdh-key.txt

Features
   * In PSA, allow using a key declared with a base key agreement algorithm
     in combined key agreement and derivation operations, as long as the key
     agreement algorithm in use matches the algorithm the key was declared with.
     This is currently non-standard behaviour, but expected to make it into a
     future revision of the PSA Crypto standard.