overlays: Update the README

Replace the use of vcdbg with vclog, and correct the documentation URL.

See: raspberrypi#7093

Signed-off-by: Phil Elwell <[email protected]>

Author: pelwell

arch/arm/boot/dts/overlays/README

@@ -5975,21 +5975,22 @@ Params: brightness              Set the initial brightness for the LEDs. The
 Troubleshooting
 ===============
 
-If you are experiencing problems that you think are DT-related, enable DT
-diagnostic output by adding this to /boot/config.txt:
+If you are experiencing problems that you think are DT-related, first check for
+error messages from the firmware by running:
 
-    dtdebug=on
+    sudo vclog -m
 
-and rebooting. Then run:
+To see more details about the changes to the Device Tree, add the following to
+/boot/firmware/config.txt:
 
-    sudo vcdbg log msg
+    dtdebug=on
 
-and look for relevant messages.
+and reboot, then use vclog as above.
 
 Further reading
 ===============
 
 This is only meant to be a quick introduction to the subject of Device Tree on
 Raspberry Pi. There is a more complete explanation here:
 
-http://www.raspberrypi.org/documentation/configuration/device-tree.md
+https://www.raspberrypi.com/documentation/computers/configuration.html#device-trees-overlays-and-parameters