kbuild: Re-sync DTC flag logic with v4.17

The way that we have been handling additional DTC warning flags hasn't
matched the way the Linux Kernel does.  Resync this logic with v4.17.

Signed-off-by: Tom Rini <trini@konsulko.com>

scripts/Makefile.extrawarn

@@ -56,25 +56,4 @@ endif
 
 KBUILD_CFLAGS += $(warning)
 
-dtc-warning-2 += -Wnode_name_chars_strict
-dtc-warning-2 += -Wproperty_name_chars_strict
-
-dtc-warning := $(dtc-warning-$(findstring 1, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
-dtc-warning += $(dtc-warning-$(findstring 2, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
-dtc-warning += $(dtc-warning-$(findstring 3, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
-
-DTC_FLAGS += $(dtc-warning)
-
-else
-
-# Disable noisy checks by default
-DTC_FLAGS += -Wno-unit_address_vs_reg
-DTC_FLAGS += -Wno-simple_bus_reg
-DTC_FLAGS += -Wno-unit_address_format
-DTC_FLAGS += -Wno-pci_bridge
-DTC_FLAGS += -Wno-pci_device_bus_num
-DTC_FLAGS += -Wno-pci_device_reg
-DTC_FLAGS += -Wno-avoid_unnecessary_addr_size
-DTC_FLAGS += -Wno-alias_paths
-
 endif

scripts/Makefile.lib

@@ -274,6 +274,22 @@ cmd_gzip = (cat $(filter-out FORCE,$^) | gzip -n -f -9 > $@) || \
 # DTC
 # ---------------------------------------------------------------------------
 
+# Disable noisy checks by default
+ifeq ($(findstring 1,$(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
+DTC_FLAGS += -Wno-unit_address_vs_reg \
+	-Wno-unit_address_format \
+	-Wno-avoid_unnecessary_addr_size \
+	-Wno-alias_paths \
+	-Wno-pci_device_reg
+endif
+
+ifneq ($(findstring 2,$(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
+DTC_FLAGS += -Wnode_name_chars_strict \
+	-Wproperty_name_chars_strict
+endif
+
+DTC_FLAGS += $(DTC_FLAGS_$(basetarget))
+
 # Generate an assembly file to wrap the output of the device tree compiler
 quiet_cmd_dt_S_dtb= DTB     $@
 # Modified for U-Boot