I have seen that the crypto service has been migrated to mbedcrypto implementation, but at the same time, the crypto engine layer has been removed from the crypto service.
Is there the new plan to add the engine layer again based on the mbedcrypto implementation?
the functionalities that were implemented through the crypto engine layer are now part of the functionalities which are provided directly by mbedcrypto. In particular, mbedcrypto is developing a driver model to allow seamless integration of crypto accelerators and secure elements which comply to the interface specified by the crypto driver model. This is still under development and not part of the mbedcrypto version supported by TF-M.
More details are available directly from the Mbed Crypto repository, in https://github.com/ARMmbed/mbed-crypto/tree/development/include/psa, in particular in crypto_accel_driver.h and crypto_se_driver.h, and in the PDF description here: https://github.com/ARMmbed/mbed-crypto/blob/development/docs/PSACryptoDriverModelSpec.pdf