diff --git a/boards/vendor/custom_plank/pre_dt_board.cmake b/boards/vendor/custom_plank/pre_dt_board.cmake
new file mode 100644
index 00000000..ded6fc3f
--- /dev/null
+++ b/boards/vendor/custom_plank/pre_dt_board.cmake
@@ -0,0 +1,7 @@
+# Copyright (c) 2024 Nordic Semiconductor
+# SPDX-License-Identifier: Apache-2.0
+
+# Suppress "unique_unit_address_if_enabled" to handle the following overlaps:
+# - power@40000000 & clock@40000000 & bprot@40000000
+# - acl@4001e000 & flash-controller@4001e000
+list(APPEND EXTRA_DTC_FLAGS "-Wno-unique_unit_address_if_enabled")