Index: head/share/man/man4/fdt.4
===================================================================
--- head/share/man/man4/fdt.4
+++ head/share/man/man4/fdt.4
@@ -28,7 +28,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 12, 2010
+.Dd March 28, 2019
 .Dt FDT 4
 .Os
 .Sh NAME
@@ -139,6 +139,21 @@
 .Fx
 kernel level.
 .Bl -tag -width Ar
+.It Va makeoptions DTS+=<board name>.dts
+Specifies device tree source (DTS) files for a given kernel.
+The indicated DTS files will be converted (compiled) into a binary form
+along with building the kernel itself.
+Any DTS file names not written as an absolute path must be specified relative
+to the default location of DTS sources i.e.,
+.Pa sys/dts .
+.It Va makeoptions DTSO+=<overlay name>.dtso
+Specifies device tree source overlay (DTSO) files for a given kernel.
+Overlay files will be built with the kernel as with the makeoption
+.Va DTS
+described above.
+Overlay files specified as relative paths will be relative to the default
+location of DTS overlays for the platform being built i.e.,
+.Pa sys/dts/arm/overlays .
 .It Va options FDT
 The primary option for enabling
 .Nm
@@ -153,10 +168,9 @@
 .It Va makeoptions FDT_DTS_FILE=<board name>.dts
 Specifies a preferred (default) device tree source (DTS) file for a given
 kernel.
-The indicated DTS file will be converted (compiled) into a binary form
-along with building the kernel itself.
-The DTS file name is relative to the default location of DTS sources i.e.
-.Pa sys/dts .
+It will be built along with the kernel as if it were supplied via the makeoption
+.Va DTS
+described above.
 This makeoption is not mandatory unless FDT_DTB_STATIC is also defined (see
 below).
 .It Va options FDT_DTB_STATIC
Index: head/sys/conf/files
===================================================================
--- head/sys/conf/files
+++ head/sys/conf/files
@@ -19,17 +19,9 @@
 	compile-with	"sh $S/dev/bhnd/tools/nvram_map_gen.sh $S/dev/bhnd/nvram/nvram_map -d" \
 	no-obj no-implicit-rule before-depend				   \
 	clean		"bhnd_nvram_map_data.h"
-#
-# The 'fdt_dtb_file' target covers an actual DTB file name, which is derived
-# from the specified source (DTS) file: <platform>.dts -> <platform>.dtb
-#
-fdt_dtb_file			optional fdt fdt_dtb_static \
-	compile-with "sh -c 'MACHINE=${MACHINE} $S/tools/fdt/make_dtb.sh $S ${FDT_DTS_FILE} ${.CURDIR}'" \
-	no-obj no-implicit-rule before-depend	\
-	clean		"${FDT_DTS_FILE:R}.dtb"
 fdt_static_dtb.h		optional fdt fdt_dtb_static \
 	compile-with "sh -c 'MACHINE=${MACHINE} $S/tools/fdt/make_dtbh.sh ${FDT_DTS_FILE} ${.CURDIR}'" \
-	dependency	"fdt_dtb_file" \
+	dependency	"${FDT_DTS_FILE:T:R}.dtb" \
 	no-obj no-implicit-rule before-depend \
 	clean		"fdt_static_dtb.h"
 feeder_eq_gen.h			optional sound				   \
@@ -1723,7 +1715,7 @@
 dev/fdt/fdt_pinctrl_if.m	optional fdt fdt_pinctrl
 dev/fdt/fdt_slicer.c		optional fdt cfi | fdt nand | fdt mx25l | fdt n25q | fdt at45d
 dev/fdt/fdt_static_dtb.S	optional fdt fdt_dtb_static \
-	dependency	"fdt_dtb_file"
+	dependency	"${FDT_DTS_FILE:T:R}.dtb"
 dev/fdt/simplebus.c		optional fdt
 dev/fdt/simple_mfd.c		optional fdt
 dev/fe/if_fe.c			optional fe
Index: head/sys/conf/kern.post.mk
===================================================================
--- head/sys/conf/kern.post.mk
+++ head/sys/conf/kern.post.mk
@@ -8,6 +8,9 @@
 # should be defined in the kern.pre.mk so that port makefiles can
 # override or augment them.
 
+.if !empty(FDT_DTS_FILE)
+DTS+=			${FDT_DTS_FILE}
+.endif
 .if defined(DTS) || defined(DTSO)
 .include "dtb.build.mk"