mbedtls/ChangeLog.d/9302.txt

Features
   * When the new compilation option MBEDTLS_PSA_STATIC_KEY_SLOTS is enabled,
     key store uses statically allocated key slot's buffers instead of
     dynamically allocating them on heap memory at runtime (through malloc/free
     calls).
     The size of each buffer is given by the option
     MBEDTLS_PSA_STATIC_KEY_SLOT_BUFFER_SIZE. By default it accomodates the
     largest PSA key enabled in the build.