diff --git a/include/image.mk b/include/image.mk
index 3832b7ae84..71971e21ca 100644
--- a/include/image.mk
+++ b/include/image.mk
@@ -141,6 +141,11 @@ ifneq ($(CONFIG_NAND_SUPPORT),)
 	(cd "$(KDIR_TMP)"; $(TAR) cvf \
 		"$(BIN_DIR)/$(IMG_PREFIX)-$(1)-$(2)-sysupgrade.tar" sysupgrade-$(1))
    endef
+# $(1) board name
+# $(2) ubinize-image options (e.g. --no-kernel and/or --uboot-env)
+# $(3) rootfstype (e.g. squashfs or ubifs)
+# $(4) kernel image file
+# $(5) options to pass-through to ubinize (i.e. $($(PROFILE)_UBI_OPTS)))
    define Image/Build/UbinizeImage
 	sh $(TOPDIR)/scripts/ubinize-image.sh $(2) \
 		"$(KDIR)/root.$(3)" "$(4)" \