Add note about not implementing PSK id_hint
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 4212bb0..b778255 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1614,6 +1614,11 @@
* \note This is mainly useful for clients. Servers will usually
* want to use \c mbedtls_ssl_conf_psk_cb() instead.
*
+ * \note Currently clients can only register one pre-shared key.
+ * In other words, the servers' idendity hint is ignored.
+ * Please contact us if you need ability to set multiple PSKs
+ * on clients and select one based on the identity hint.
+ *
* \param conf SSL configuration
* \param psk pointer to the pre-shared key
* \param psk_len pre-shared key length