doc: update use-psa-crypto.md
Signed-off-by: valerio <valerio.setti@nordicsemi.no>
diff --git a/docs/use-psa-crypto.md b/docs/use-psa-crypto.md
index 9d783d5..92d0985 100644
--- a/docs/use-psa-crypto.md
+++ b/docs/use-psa-crypto.md
@@ -13,7 +13,8 @@
**Application code:** when this option is enabled, you need to call
`psa_crypto_init()` before calling any function from the SSL/TLS, X.509 or PK
-module.
+modules, except for the various mbedtls_xxx_init() functions which can be called
+at any time.
**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