x509: Reworded documentation bits.

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
diff --git a/ChangeLog.d/x509-add-ca_istrue.txt b/ChangeLog.d/x509-add-ca_istrue.txt
index 4594c22..c950dbc 100644
--- a/ChangeLog.d/x509-add-ca_istrue.txt
+++ b/ChangeLog.d/x509-add-ca_istrue.txt
@@ -1,4 +1,5 @@
 Features
    * Add new accessor to expose the `MBEDTLS_PRIVATE(ca_istrue)` member of
      `mbedtls_x509_crt` structure. This requires setting
-     MBEDTLS_X509_EXT_BASIC_CONSTRAINTS.
+     the MBEDTLS_X509_EXT_BASIC_CONSTRAINTS bit in the certificate's
+     ext_types field.
diff --git a/include/mbedtls/x509_crt.h b/include/mbedtls/x509_crt.h
index fc1d0bc..1ce0d23 100644
--- a/include/mbedtls/x509_crt.h
+++ b/include/mbedtls/x509_crt.h
@@ -922,7 +922,7 @@
  * \param[in] crt       Certificate to be queried, must not be \c NULL
  *
  * \return              \c 1 if this a CA certificate \c 0 otherwise.
- * \return              MBEDTLS_ERR_X509_INVALID_EXTENSIONS if the certificate does not support
+ * \return              MBEDTLS_ERR_X509_INVALID_EXTENSIONS if the certificate does not contain
  *                      the Optional Basic Constraint extension.
  *
  */