add port number 4238 for BTS control interface
diff --git a/include/osmocom/vty/ports.h b/include/osmocom/vty/ports.h
index 96bc60a..a58c73b 100644
--- a/include/osmocom/vty/ports.h
+++ b/include/osmocom/vty/ports.h
@@ -2,6 +2,7 @@
 
 /* TCP port numbers used for VTY interfaces in osmocom projects */
 
+/* 4238 used by osmo-bts control interface */
 #define OSMO_VTY_PORT_PCU	4240	/* also: osmo_pcap_client */
 #define OSMO_VTY_PORT_BTS	4241	/* also: osmo_pcap_server */
 #define OSMO_VTY_PORT_NITB_BSC	4242