media: docs: move uAPI book to userspace-api/media

Since 2017, there is an space reserved for userspace API,
created by changeset 1d596dee3862 ("docs: Create a user-space API guide").

As the media subsystem was one of the first subsystems to use
Sphinx, until this patch, we were keeping things on a separate
place.

Let's just use the new location, as having all uAPI altogether
will likely make things easier for developers.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
diff --git a/Documentation/Makefile b/Documentation/Makefile
index cc786d1..7e12d10 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -55,15 +55,15 @@
 loop_cmd = $(echo-cmd) $(cmd_$(1)) || exit;
 
 # $2 sphinx builder e.g. "html"
-# $3 name of the build subfolder / e.g. "media", used as:
+# $3 name of the build subfolder / e.g. "userspace-api/media", used as:
 #    * dest folder relative to $(BUILDDIR) and
 #    * cache folder relative to $(BUILDDIR)/.doctrees
-# $4 dest subfolder e.g. "man" for man pages at media/man
+# $4 dest subfolder e.g. "man" for man pages at userspace-api/media/man
 # $5 reST source folder relative to $(srctree)/$(src),
-#    e.g. "media" for the linux-tv book-set at ./Documentation/media
+#    e.g. "userspace-api/media" for the linux-tv book-set at ./Documentation/userspace-api/media
 
 quiet_cmd_sphinx = SPHINX  $@ --> file://$(abspath $(BUILDDIR)/$3/$4)
-      cmd_sphinx = $(MAKE) BUILDDIR=$(abspath $(BUILDDIR)) $(build)=Documentation/media $2 && \
+      cmd_sphinx = $(MAKE) BUILDDIR=$(abspath $(BUILDDIR)) $(build)=Documentation/userspace-api/media $2 && \
 	PYTHONDONTWRITEBYTECODE=1 \
 	BUILDDIR=$(abspath $(BUILDDIR)) SPHINX_CONF=$(abspath $(srctree)/$(src)/$5/$(SPHINX_CONF)) \
 	$(PYTHON) $(srctree)/scripts/jobserver-exec \
@@ -120,7 +120,7 @@
 
 cleandocs:
 	$(Q)rm -rf $(BUILDDIR)
-	$(Q)$(MAKE) BUILDDIR=$(abspath $(BUILDDIR)) $(build)=Documentation/media clean
+	$(Q)$(MAKE) BUILDDIR=$(abspath $(BUILDDIR)) $(build)=Documentation/userspace-api/media clean
 
 dochelp:
 	@echo  ' Linux kernel internal documentation in different formats from ReST:'