[doc] make sure all SMS related code is part of the 'sms' group

Change-Id: I24c56ccb56d5b39cfb887808f91b715da54c0f8b
diff --git a/include/osmocom/gsm/gsm0341.h b/include/osmocom/gsm/gsm0341.h
index 2fc83e4..834dbf9 100644
--- a/include/osmocom/gsm/gsm0341.h
+++ b/include/osmocom/gsm/gsm0341.h
@@ -1,4 +1,6 @@
-/*! \file gsm0341.h */
+/*! \defgroup sms Short Message Service (SMS)
+ *  @{
+ * \file gsm0341.h */
 
 #pragma once
 
@@ -9,3 +11,5 @@
 		  uint8_t update, uint16_t msg_id, uint8_t dcs,
 		  uint8_t page_total, uint8_t page_cur,
 		  uint8_t *data, uint8_t len);
+
+/*! @} */
diff --git a/include/osmocom/gsm/gsm0411_smc.h b/include/osmocom/gsm/gsm0411_smc.h
index 0cd1f94..7dfaa15 100644
--- a/include/osmocom/gsm/gsm0411_smc.h
+++ b/include/osmocom/gsm/gsm0411_smc.h
@@ -1,4 +1,6 @@
-/*! \file gsm0411_smc.h */
+/*! \addtogroup sms
+ *  @{
+ *  \file gsm0411_smc.h */
 
 #pragma once
 
@@ -61,3 +63,5 @@
 /* message from lower layer */
 int gsm411_smc_recv(struct gsm411_smc_inst *inst, int msg_type,
 	struct msgb *msg, int cp_msg_type);
+
+/*! @} */
diff --git a/include/osmocom/gsm/gsm0411_smr.h b/include/osmocom/gsm/gsm0411_smr.h
index 19f9c5d..28f43de 100644
--- a/include/osmocom/gsm/gsm0411_smr.h
+++ b/include/osmocom/gsm/gsm0411_smr.h
@@ -1,4 +1,6 @@
-/*! \file gsm0411_smr.h */
+/*! \addtogroup sms
+ *  @{
+ * \file gsm0411_smr.h */
 
 #pragma once
 
@@ -42,3 +44,5 @@
 /* message from lower layer */
 int gsm411_smr_recv(struct gsm411_smr_inst *inst, int msg_type,
 	struct msgb *msg);
+
+/*! @} */
diff --git a/include/osmocom/gsm/gsm0411_utils.h b/include/osmocom/gsm/gsm0411_utils.h
index 1c51111..2cd87b8 100644
--- a/include/osmocom/gsm/gsm0411_utils.h
+++ b/include/osmocom/gsm/gsm0411_utils.h
@@ -1,4 +1,6 @@
-/*! \file gsm0411_utils.h */
+/*! \addtogroup sms
+ *  @{
+ * \file gsm0411_utils.h */
 
 #pragma once
 
@@ -35,3 +37,5 @@
 /* Prefix msg with a 04.08/04.11 CP header */
 int gsm411_push_cp_header(struct msgb *msg, uint8_t proto, uint8_t trans,
 			     uint8_t msg_type);
+
+/*! @} */