This parameter is there for some time, but it doesn't have anything
documenting it at make help.

Add some documentation, pointing to the place where one can find
more details.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
 Documentation/Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Documentation/Makefile b/Documentation/Makefile
index a52b311cdadc..05397b9d844d 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -126,4 +126,7 @@ dochelp:
 	@echo
 	@echo  '  make PAPER={a4|letter} Specifies the paper size used for LaTeX/PDF output.'
 	@echo
+	@echo  '  make FONTS_CONF_DENY_VF={path} sets a deny list to block variable Noto CJK fonts'
+	@echo  '  for PDF build. See tools/docs/lib/latex_fonts.py for more details'
+	@echo
 	@echo  '  Default location for the generated documents is Documentation/output'
-- 
2.51.0