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/configs/porter_defconfig b/configs/porter_defconfig
new file mode 100644
index 0000000..8d594d9
--- /dev/null
+++ b/configs/porter_defconfig
@@ -0,0 +1,6 @@
+CONFIG_ARM=y
+CONFIG_RMOBILE=y
+CONFIG_TARGET_PORTER=y
+CONFIG_DM=y
+CONFIG_DM_SERIAL=y
+CONFIG_SH_SDHI=y