diff --git a/src/platform/nm-platform.c b/src/platform/nm-platform.c
index 7e91b7547d..1b47702cc6 100644
--- a/src/platform/nm-platform.c
+++ b/src/platform/nm-platform.c
@@ -3778,6 +3778,10 @@ _ip_route_scope_inv_get_normalized (const NMPlatformIP4Route *route)
  * Adding a route to kernel via nm_platform_ip_route_add() will normalize/coerce some
  * properties of the route. This function modifies (normalizes) the route like it
  * would be done by adding the route in kernel.
+ *
+ * Note that this function is related to NM_PLATFORM_IP_ROUTE_CMP_TYPE_SEMANTICALLY
+ * in that if two routes compare semantically equal, after normalizing they also shall
+ * compare equal with NM_PLATFORM_IP_ROUTE_CMP_TYPE_FULL.
  */
 void
 nm_platform_ip_route_normalize (int addr_family,
diff --git a/src/platform/nm-platform.h b/src/platform/nm-platform.h
index b29e6668d2..a703d4c879 100644
--- a/src/platform/nm-platform.h
+++ b/src/platform/nm-platform.h
@@ -138,7 +138,10 @@ typedef enum {
 	 * a route destination 192.168.1.5/24 is not accepted by kernel and
 	 * we treat it identical to 192.168.1.0/24. Semantically these
 	 * routes are identical, but NM_PLATFORM_IP_ROUTE_CMP_TYPE_FULL will
-	 * report them as different. */
+	 * report them as different.
+	 *
+	 * The result shall be identical to call first nm_platform_ip_route_normalize()
+	 * on both routes and then doing a full comparison. */
 	NM_PLATFORM_IP_ROUTE_CMP_TYPE_SEMANTICALLY,
 
 	/* compare all fields. This should have the same effect as memcmp(),