Add dtb overlays support

DTB Overlays are useful to change/add nodes to a dtb without the need to
modify it.
Add support for building dtbo during buildkernel.
The goal of DTBO present in the FreeBSD source tree is to fill a gap in
time when we submit changes upstream (Linux). Instead of waiting 2 to 4 months
we can add a DTBO in tree in the meantime.
This is not for adding DTBO for capes/hat/addon boards, those will be
better to put in a ports.
This is also not for enabling a i2c/spi/pwm controller on certain pins,
each user have a different use case for those (which pins to use etc ...)
and we cannot have all possible configuration.

Add a dtbo for sun8i-h3-sid which add the SID node missing in upstream dts.

Reviewed by:	kevans
Differential Revision:	https://reviews.freebsd.org/D14782

1 files changed, 26 insertions, 0 deletions

diff --git a/sys/tools/fdt/make_dtbo.sh b/sys/tools/fdt/make_dtbo.sh
new file mode 100755
index 000000000000..3a438ac5d5aa
--- /dev/null
+++ b/sys/tools/fdt/make_dtbo.sh
@@ -0,0 +1,26 @@
+#!/bin/sh
+#
+# $FreeBSD$
+
+# Script generates dtbo file ($3) from dtso source ($2) in build tree S ($1)
+S=$1
+dtso="$2"
+dtbo_path=$3
+
+if [ -z "$dtso" ]; then
+    echo "No DTS overlays specified"
+    exit 1
+fi
+
+if [ -z "${MACHINE}" ]; then
+    MACHINE=$(uname -m)
+fi
+
+: ${DTC:=dtc}
+
+for d in ${dtso}; do
+    dtb=${dtbo_path}/`basename $d .dtso`.dtbo
+    echo "converting $d -> $dtb"
+    cpp -P -x assembler-with-cpp -I $S/gnu/dts/include -I $S/dts/${MACHINE} -I $S/gnu/dts/${MACHINE} -include $d /dev/null | 
+	${DTC} -@ -O dtb -o $dtb -i $S/dts/${MACHINE} -i $S/gnu/dts/${MACHINE}
+done