arm: rmobile: Add Porter board support

Porter is an entry level development board based on R-Car M2 SoC (R8A7791)

This commit supports the following peripherals:
- SCIF, I2C, Ethernet, QSPI, SD, USB Host

Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/board/renesas/porter/MAINTAINERS b/board/renesas/porter/MAINTAINERS
new file mode 100644
index 0000000..1dc6a1c
--- /dev/null
+++ b/board/renesas/porter/MAINTAINERS
@@ -0,0 +1,6 @@
+PORTER BOARD
+M:	Cogent Embedded, Inc. <source@cogentembedded.com>
+S:	Maintained
+F:	board/renesas/porter/
+F:	include/configs/porter.h
+F:	configs/porter_defconfig