[nrf fromlist] scripts: gen_dts_cmake: Support variable target name in dts.cmake

Upstream PR: zephyrproject-rtos/zephyr#73903

Instead of hardcoding the name `devicetree_target`, we can update the
generated `dts.cmake` to accept `DEVICETREE_TARGET` as input variable.
This will become useful in multi-image builds, where we would like to
process multiple devicetrees.

Signed-off-by: Grzegorz Swiderski <[email protected]>
(cherry picked from commit cd187c719ae9162a2ab6bd6aeff511a4cc684bdc)

Author: 57300

cmake/modules/dts.cmake

@@ -117,6 +117,8 @@ set(GEN_DTS_CMAKE_SCRIPT        ${DT_SCRIPTS}/gen_dts_cmake.py)
 # The generated information itself, which we include() after
 # creating it.
 set(DTS_CMAKE                   ${PROJECT_BINARY_DIR}/dts.cmake)
+# The CMake target to be initialized by including ${DTS_CMAKE}.
+set(DEVICETREE_TARGET           devicetree_target)
 
 # The location of a file containing known vendor prefixes, relative to
 # each element of DTS_ROOT. Users can define their own in their own

scripts/dts/gen_dts_cmake.py

@@ -11,12 +11,13 @@
 
 The generated CMake file looks like this:
 
-  add_custom_target(devicetree_target)
-  set_target_properties(devicetree_target PROPERTIES
+  add_custom_target(${DEVICETREE_TARGET})
+  set_target_properties(${DEVICETREE_TARGET} PROPERTIES
                         "DT_PROP|/soc|compatible" "vnd,soc;")
   ...
 
-It defines a special CMake target, and saves various values in the
+It takes an input variable - DEVICETREE_TARGET - and creates a special
+CMake target with this name, which will contain various values in the
 devicetree as CMake target properties.
 
 Be careful:
@@ -154,15 +155,13 @@ def main():
         cmake_comp = f'DT_COMP|{comp}'
         cmake_props.append(f'"{cmake_comp}" "{cmake_path}"')
 
+    cmake_props = map(
+        'set_target_properties(${{DEVICETREE_TARGET}} PROPERTIES {})'.format,
+        cmake_props
+    )
     with open(args.cmake_out, "w", encoding="utf-8") as cmake_file:
-        print('add_custom_target(devicetree_target)', file=cmake_file)
-        print(file=cmake_file)
-
-        for prop in cmake_props:
-            print(
-                f'set_target_properties(devicetree_target PROPERTIES {prop})',
-                file=cmake_file
-            )
+        print('add_custom_target(${DEVICETREE_TARGET})\n', *cmake_props,
+              sep='\n', file=cmake_file)
 
 
 if __name__ == "__main__":