diff --git a/cmake/dts.cmake b/cmake/dts.cmake
index 0c9d990c804..f41e1aebd44 100644
--- a/cmake/dts.cmake
+++ b/cmake/dts.cmake
@@ -140,6 +140,7 @@ if(SUPPORTS_DTS)
     ${DTC_INCLUDE_FLAG_FOR_DTS}  # include the DTS source and overlays
     ${NOSYSDEF_CFLAG}
     -D__DTS__
+    ${DTS_EXTRA_CPPFLAGS}
     -P
     -E   # Stop after preprocessing
     -MD  # Generate a dependency file as a side-effect
diff --git a/doc/application/index.rst b/doc/application/index.rst
index d4965439a76..bac3044b5e0 100644
--- a/doc/application/index.rst
+++ b/doc/application/index.rst
@@ -783,6 +783,20 @@ You can also define the variable in the application :file:`CMakeLists.txt`
 file. Make sure to do so **before** pulling in the Zephyr boilerplate with
 ``find_package(Zephyr ...)``.
 
+Devicetree source are passed through the C preprocessor, so you can
+include files that can be located in a ``DTS_ROOT`` directory.  By
+convention devicetree include files have a ``.dtsi`` extension.
+
+You can also use the preprocessor to control the content of a devicetree
+file, by specifying directives through the ``DTS_EXTRA_CPPFLAGS`` CMake
+Cache variable:
+
+.. zephyr-app-commands::
+   :tool: all
+   :board: <board name>
+   :gen-args: -DDTS_EXTRA_CPPFLAGS=-DTEST_ENABLE_FEATURE
+   :goals: build
+   :compact:
 
 Application Debugging
 *********************