Update documentation to mention ECC drivers

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/docs/use-psa-crypto.md b/docs/use-psa-crypto.md
index 4d72f99..305dd73 100644
--- a/docs/use-psa-crypto.md
+++ b/docs/use-psa-crypto.md
@@ -15,6 +15,13 @@
 `psa_crypto_init()` before calling any function from the SSL/TLS, X.509 or PK
 module.
 
+**Why enable this option:** to fully take advantage of PSA drivers in PK,
+X.509 and TLS. For example, enabling this option is what allows use of drivers
+for ECDSA, ECDH and EC J-PAKE in those modules. However, note that ven with
+this option disabled, some code in PK, X.509, TLS or the crypto library might
+still use PSA drivers, if it can determine it's safe to do so; currently
+that's the case for hashes.
+
 **Relationship with other options:** This option depends on
 `MBEDTLS_PSA_CRYPTO_C`. These two options differ in the following way:
 - `MBEDTLS_PSA_CRYPTO_C` enables the implementation of the PSA Crypto API.
diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index ef3cf24..3209281 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -1933,9 +1933,12 @@
  * \warning If you enable this option, you need to call `psa_crypto_init()`
  * before calling any function from the SSL/TLS, X.509 or PK modules.
  *
- * \note Even with this option disabled, some code in PK, X.509, TLS or the
- * crypto library might still use PSA drivers, if it can determine it's safe
- * to do so.
+ * \note An important and desirable effect of this option is that it allows
+ * PK, X.509 and TLS to take advantage of PSA drivers. For example, enabling
+ * this option is what allows use of drivers for ECDSA, ECDH and EC J-PAKE in
+ * those modules. However, note that ven with this option disabled, some code
+ * in PK, X.509, TLS or the crypto library might still use PSA drivers, if it
+ * can determine it's safe to do so; currently that's the case for hashes.
  *
  * \note See docs/use-psa-crypto.md for a complete description this option.
  *