diff --git a/include/mbedtls/x509_crt.h b/include/mbedtls/x509_crt.h
index 06166d8..c589a5e 100644
--- a/include/mbedtls/x509_crt.h
+++ b/include/mbedtls/x509_crt.h
@@ -286,8 +286,15 @@
  *                 used to sign the certificate, CRL verification is skipped
  *                 silently, that is *without* setting any flag.
  *
+ * \note           The \c trust_ca list can contain two type of certificates:
+ *                 (1) those of trusted root CAs, so that certificates
+ *                 chaining up to those CAs will be trusted, and (2)
+ *                 self-signed end-entity certificates to be trusted (for
+ *                 specific peers you know) - in that case, the self-signed
+ *                 certificate doens't need to have the CA bit set.
+ *
  * \param crt      a certificate (chain) to be verified
- * \param trust_ca the list of trusted CAs
+ * \param trust_ca the list of trusted CAs (see note above)
  * \param ca_crl   the list of CRLs for trusted CAs (see note above)
  * \param cn       expected Common Name (can be set to
  *                 NULL if the CN must not be verified)