[PATCH] [RFC] dt-bindings: Consider DT_SCHEMA_FILES when finding all json-schema

Setting DT_SCHEMA_FILES allows the user to restrict the
"dt_binding_check" make target to a specified set of DT binding files.
However, yamllint is still run on all available files, which can take
quite some time.

Fix this by changing "find_cmd" to only return the specified files.
Note that this also affects the "cmd_chk_bindings" and "cmd_mk_schema"
rules.

This reduces the execution time of

    make dt_binding_check DT_SCHEMA_FILES=/path/to/json/schema/file

from ca. 22 to less than 2 seconds on an i7-8700K.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
Should this be restricted to cmd_yamllint?
I'm not sure which users of find_cmd do and do not need all files.
---
 Documentation/devicetree/bindings/Makefile | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Documentation/devicetree/bindings/Makefile b/Documentation/devicetree/bindings/Makefile
index 780e5618ec0ae2fc..60ac03bade2da0ad 100644
--- a/Documentation/devicetree/bindings/Makefile
+++ b/Documentation/devicetree/bindings/Makefile

@@ -22,10 +22,18 @@ $(obj)/%.example.dts: $(src)/%.yaml check_dtschema_version FORCE
 # Use full schemas when checking %.example.dts
 DT_TMP_SCHEMA := $(obj)/processed-schema-examples.json
 
+ifeq ($(DT_SCHEMA_FILES),)
+
 find_cmd = find $(srctree)/$(src) \( -name '*.yaml' ! \
 		-name 'processed-schema*' ! \
 		-name '*.example.dt.yaml' \)
 
+else
+
+find_cmd = echo $(addprefix $(srctree)/, $(DT_SCHEMA_FILES))
+
+endif
+
 quiet_cmd_yamllint = LINT    $(src)
       cmd_yamllint = ($(find_cmd) | \
                      xargs $(DT_SCHEMA_LINT) -f parsable -c $(srctree)/$(src)/.yamllint) || true

-- 
2.25.1