of: update kconfig unittest help

Add more information about the impact the of unittests have on the
live devicetree and why the tests should only be enabled for developer
kernels.

Add information about processing the test output such that the
results are more complete and comprehendable.
Signed-off-by: Frank Rowand <frowand.list@gmail.com>
Link: https://lore.kernel.org/r/20230213185702.395776-4-frowand.list@gmail.comSigned-off-by: Rob Herring <robh@kernel.org>

drivers/of/Kconfig

@@ -23,7 +23,19 @@ config OF_UNITTEST
 	  that are executed once at boot time, and the results dumped to the
 	  console.
 
-	  If unsure, say N here, but this option is safe to enable.
+	  This option should only be enabled for a development kernel. The tests
+	  will taint the kernel with TAINT_TEST. The tests will cause ERROR and
+	  WARNING messages to print on the console. The tests will cause stack
+	  traces to print on the console.  It is possible that the tests will
+	  leave the devicetree in a corrupted state.
+
+	  The unittest output will be verbose.  Copy the output to a file
+	  via capturing the console output or via the dmesg command.  Process
+	  this file with scripts/dtc/of_unittest_expect to reduce the
+	  verbosity, test whether expected output is present, and to
+	  summarize the results.
+
+	  If unsure, say N here. This option is not safe to enable.
 
 config OF_ALL_DTBS
 	bool "Build all Device Tree Blobs"