doc: net: Hide UDP API documentation

The UDP API functions are for Zephyr internal use only so do
not generate documentation for them.

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>

doc/reference/networking/index.rst

@@ -31,4 +31,3 @@ Networking
    ptp_time.rst
    traffic-class.rst
    trickle.rst
-   udp.rst

doc/reference/networking/udp.rst

@@ -1,14 +0,0 @@
-.. _udp_interface:
-
-UDP
-###
-
-Overview
-********
-
-
-API Reference
-*************
-
-.. doxygengroup:: udp
-   :project: Zephyr

include/net/udp.h

@@ -21,6 +21,11 @@
 extern "C" {
 #endif
 
+/* These APIs are mostly meant for Zephyr internal use so do not generate
+ * documentation for them.
+ */
+/** @cond INTERNAL_HIDDEN */
+
 /**
  * @brief UDP library
  * @defgroup udp UDP Library
@@ -86,6 +91,8 @@ static inline struct net_udp_hdr *net_udp_set_hdr(struct net_pkt *pkt,
  * @}
  */
 
+/** @endcond */
+
 #ifdef __cplusplus
 }
 #endif