[knx] Minor documentation update (openhab#13918)

Slightly change wording of docs related to localSourceAddress to avoid
address conflicts during initial setup.
Add remark about knxd.
Fixes openhab#13602.

Signed-off-by: Holger Friedrich <[email protected]>
Signed-off-by: Andras Uhrin <[email protected]>

bundles/org.openhab.binding.knx/README.md

@@ -33,7 +33,7 @@ The IP Gateway is the most commonly used way to connect to the KNX bus. At its b
 | ipAddress           | for `TUNNEL` | Network address of the KNX/IP gateway. If type `ROUTER` is set, the IPv4 Multicast Address can be set.       | for `TUNNEL`: \<nothing\>, for `ROUTER`: 224.0.23.12 |
 | portNumber          | for `TUNNEL` | Port number of the KNX/IP gateway                                                                            | 3671                                                 |
 | localIp             | No           | Network address of the local host to be used to set up the connection to the KNX/IP gateway                  | the system-wide configured primary interface address |
-| localSourceAddr     | No           | The (virtual) individual address for identification of this KNX/IP gateway within the KNX bus <br/><br/>Note: Use a free address, not the one of the interface. Or leave it at `0.0.0` and let openHAB decide which address to use.                | 0.0.0                                                |
+| localSourceAddr     | No           | The (virtual) individual address for identification of this openHAB Thing within the KNX bus <br/><br/>Note: Use a free address, not the one of the interface. Or leave it at `0.0.0` and let openHAB decide which address to use. When using knxd, make sure _not to use_ one of the addresses reserved for tunneling clients.  | 0.0.0                                                |
 | useNAT              | No           | Whether there is network address translation between the server and the gateway                              | false                                                |
 | readingPause        | No           | Time in milliseconds of how long should be paused between two read requests to the bus during initialization | 50                                                   |
 | responseTimeout     | No           | Timeout in seconds to wait for a response from the KNX bus                                                   | 10                                                   |