dt-bindings: Add a minimum version check for dtschema

The dtschema package must be somewhat up to date as the tools and
meta-schema checks are still evolving. Implement a version check,
so this can be enforced. This will help ensure new schema submissions
get checked against the latest meta-schemas.
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/Makefile

@@ -4,11 +4,19 @@ DT_EXTRACT_EX ?= dt-extract-example
 DT_MK_SCHEMA ?= dt-mk-schema
 DT_MK_SCHEMA_USERONLY_FLAG := $(if $(DT_SCHEMA_FILES), -u)
 
+DT_SCHEMA_MIN_VERSION = 2020.5
+
+PHONY += check_dtschema_version
+check_dtschema_version:
+	@{ echo $(DT_SCHEMA_MIN_VERSION); \
+	$(DT_DOC_CHECKER) --version 2>/dev/null || echo 0; } | sort -VC || \
+	{ echo "ERROR: dtschema minimum version is v$(DT_SCHEMA_MIN_VERSION)" >&2; false; }
+
 quiet_cmd_chk_binding = CHKDT   $(patsubst $(srctree)/%,%,$<)
       cmd_chk_binding = $(DT_DOC_CHECKER) -u $(srctree)/$(src) $< ; \
                         $(DT_EXTRACT_EX) $< > $@
 
-$(obj)/%.example.dts: $(src)/%.yaml FORCE
+$(obj)/%.example.dts: $(src)/%.yaml check_dtschema_version FORCE
 	$(call if_changed,chk_binding)
 
 # Use full schemas when checking %.example.dts
@@ -37,11 +45,11 @@ override DTC_FLAGS := \
 	-Wno-avoid_unnecessary_addr_size \
 	-Wno-graph_child_address
 
-$(obj)/processed-schema-examples.yaml: $(DT_DOCS) FORCE
+$(obj)/processed-schema-examples.yaml: $(DT_DOCS) check_dtschema_version FORCE
 	$(call if_changed,mk_schema)
 
 $(obj)/processed-schema.yaml: DT_MK_SCHEMA_FLAGS := $(DT_MK_SCHEMA_USERONLY_FLAG)
-$(obj)/processed-schema.yaml: $(DT_SCHEMA_FILES) FORCE
+$(obj)/processed-schema.yaml: $(DT_SCHEMA_FILES) check_dtschema_version FORCE
 	$(call if_changed,mk_schema)
 
 extra-y += processed-schema.yaml