Kbuild fixes for v5.6 (2nd)

- fix missed rebuild of DT schema check
 
  - add some phony targets to PHONY
 
  - fix comments and documents
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Merge tag 'kbuild-fixes-v5.6-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild fixes from Masahiro Yamada:

 - fix missed rebuild of DT schema check

 - add some phony targets to PHONY

 - fix comments and documents

* tag 'kbuild-fixes-v5.6-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kbuild: get rid of trailing slash from subdir- example
  kbuild: add dt_binding_check to PHONY in a correct place
  kbuild: add dtbs_check to PHONY
  kbuild: remove unneeded semicolon at the end of cmd_dtb_check
  kbuild: fix DT binding schema rule to detect command line changes
  kbuild: remove wrong documentation about mandatory-y
  kbuild: add comment for V=2 mode

Documentation/kbuild/makefiles.rst

@@ -765,7 +765,7 @@ is not sufficient this sometimes needs to be explicit.
 	Example::
 
 		#arch/x86/boot/Makefile
-		subdir- := compressed/
+		subdir- := compressed
 
 The above assignment instructs kbuild to descend down in the
 directory compressed/ when "make clean" is executed.
@@ -1379,9 +1379,6 @@ See subsequent chapter for the syntax of the Kbuild file.
 	in arch/$(ARCH)/include/(uapi/)/asm, Kbuild will automatically generate
 	a wrapper of the asm-generic one.
 
-	The convention is to list one subdir per line and
-	preferably in alphabetic order.
-
 8 Kbuild Variables
 ==================
 

Makefile

@@ -68,6 +68,7 @@ unexport GREP_OPTIONS
 #
 # If KBUILD_VERBOSE equals 0 then the above command will be hidden.
 # If KBUILD_VERBOSE equals 1 then the above command is displayed.
+# If KBUILD_VERBOSE equals 2 then give the reason why each target is rebuilt.
 #
 # To put more focus on warnings, be less verbose as default
 # Use 'make V=1' to see the full commands
@@ -1238,7 +1239,7 @@ ifneq ($(dtstree),)
 %.dtb: include/config/kernel.release scripts_dtc
 	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
 
-PHONY += dtbs dtbs_install dt_binding_check
+PHONY += dtbs dtbs_install dtbs_check
 dtbs dtbs_check: include/config/kernel.release scripts_dtc
 	$(Q)$(MAKE) $(build)=$(dtstree)
 
@@ -1258,6 +1259,7 @@ PHONY += scripts_dtc
 scripts_dtc: scripts_basic
 	$(Q)$(MAKE) $(build)=scripts/dtc
 
+PHONY += dt_binding_check
 dt_binding_check: scripts_dtc
 	$(Q)$(MAKE) $(build)=Documentation/devicetree/bindings
 

scripts/Makefile.lib

@@ -300,15 +300,15 @@ DT_BINDING_DIR := Documentation/devicetree/bindings
 DT_TMP_SCHEMA := $(objtree)/$(DT_BINDING_DIR)/processed-schema.yaml
 
 quiet_cmd_dtb_check =	CHECK   $@
-      cmd_dtb_check =	$(DT_CHECKER) -u $(srctree)/$(DT_BINDING_DIR) -p $(DT_TMP_SCHEMA) $@ ;
+      cmd_dtb_check =	$(DT_CHECKER) -u $(srctree)/$(DT_BINDING_DIR) -p $(DT_TMP_SCHEMA) $@
 
-define rule_dtc_dt_yaml
+define rule_dtc
 	$(call cmd_and_fixdep,dtc,yaml)
 	$(call cmd,dtb_check)
 endef
 
 $(obj)/%.dt.yaml: $(src)/%.dts $(DTC) $(DT_TMP_SCHEMA) FORCE
-	$(call if_changed_rule,dtc_dt_yaml)
+	$(call if_changed_rule,dtc)
 
 dtc-tmp = $(subst $(comma),_,$(dot-target).dts.tmp)