Update overlay example and tool dependency

Signed-off-by: Erik Jaegervall <[email protected]>

CHANGELOG.md

@@ -228,6 +228,13 @@ What to do if you as of today use signals from the OBD file:
 * If you really need the signals in this file and cannot replace them, then consider using the overlay file in the
   `overlays` directory from VSS 6.0 onwards.
 
+### Update tool dependency
+
+#### Overlay Support
+
+VSS-tools support for overlays have been improved. It is now in many cases not necessary to specify
+`type`and `datatype` for items in the overlay if you are changing an existing item.
+
 ## Planned Changes VSS 6.0
 
 ### OBD Branch removed

docs-gen/content/rule_set/overlay.md

@@ -92,6 +92,28 @@ Vehicle.Cabin.Door.IsOpen:
 ```
 *File: overlay_2.vspec*
 
+### Node content in Overlays
+
+If you are adding a node you need to specify all attributes required for that node type.
+If you are changing an existing node you typically only need to specify name and what is changed,
+like in the `Vehicle.Speed` example below.
+Vss-tools will then look up the node name and reuse existing definitions.
+An exception is if you are changing a node for a particular instance.
+In that case you need to give `type`and `datatype`even if they are not changed,
+as the lookup mechanism currently cannot extract them from the existing definition.
+
+```YAML
+# Type and Datatype not needed
+Vehicle.Speed:
+  unit: m/s
+
+# Type and Datatype not needed as overlay affects a particular instance
+Vehicle.Occupant.Row1.DriverSide.HeadPosition.Yaw:
+  type: sensor
+  datatype: float
+  unit: mm
+```
+
 ### Overlays in the standard catalog
 
 With the feature of overlays, we introduced a new folder in the