mgcp_client: add docstring for mgcp_client_rtpbridge_wildcard()

Change-Id: I2d811b6ddda5b330054145abff37c996c54c3e3a
diff --git a/src/libosmo-mgcp-client/mgcp_client.c b/src/libosmo-mgcp-client/mgcp_client.c
index 54db20d..819461d 100644
--- a/src/libosmo-mgcp-client/mgcp_client.c
+++ b/src/libosmo-mgcp-client/mgcp_client.c
@@ -892,6 +892,9 @@
 	return endpoint;
 }
 
+/*! Compose endpoint name for a wildcarded request to the virtual trunk
+ *  \param[in] mgcp MGCP client descriptor.
+ *  \returns string containing the endpoint name (e.g. rtpbridge\*@mgw) */
 const char *mgcp_client_rtpbridge_wildcard(const struct mgcp_client *mgcp)
 {
 	return _mgcp_client_name_append_domain(mgcp, "rtpbridge/*");