parser data DOC improve out parameter description

Refs sysrepo/sysrepo#2467
diff --git a/src/parser_data.h b/src/parser_data.h
index fbb9a48..04d9b8a 100644
--- a/src/parser_data.h
+++ b/src/parser_data.h
@@ -342,7 +342,7 @@
  * @param[in] format Expected format of the data in @p in.
  * @param[in] data_type Expected operation to parse (@ref datatype).
  * @param[out] tree Optional full parsed data tree. If @p parent is set, set to NULL.
- * @param[out] op Optional parsed operation node.
+ * @param[out] op Optional pointer to the operation (action/RPC) node.
  * @return LY_ERR value.
  * @return LY_ENOT if @p data_type is a NETCONF message and the root XML element is not the expected one.
  */
@@ -385,7 +385,7 @@
  * @param[in] format Expected format of the data in @p in.
  * @param[in] data_type Expected operation to parse (@ref datatype).
  * @param[out] tree Optional full parsed data tree. If @p parent is set, set to NULL.
- * @param[out] op Optional parsed operation node.
+ * @param[out] op Optional pointer to the operation (action/RPC) node.
  * @return LY_ERR value.
  * @return LY_ENOT if @p data_type is a NETCONF message and the root XML element is not the expected one.
  */