docs: improve Doxygen comments.

refs: #1435

Change-Id: I21624ef4eec393c82a50229a07e8277fb6ae4ddf
diff --git a/src/route/nexthop-list.hpp b/src/route/nexthop-list.hpp
index be0c144..0c57ba3 100644
--- a/src/route/nexthop-list.hpp
+++ b/src/route/nexthop-list.hpp
@@ -45,9 +45,22 @@
   {
   }
 
+
+  /*! \brief Adds a next hop to the list.
+    \param nh The next hop.
+
+    Add next hop to the Next Hop list If next hop is new it is added
+    If next hop already exists in next hop list then updates the route
+    cost with new next hop's route cost
+  */
   void
   addNextHop(NextHop& nh);
 
+  /*! \brief Removes a next hop.
+    \param nh The next hop.
+
+    Remove a next hop only if both next hop face and route cost are same.
+  */
   void
   removeNextHop(NextHop& nh);