arm: imx8m: add support for Advantech RSB-3720

Add initial support for Advantech RSB-3720 board.
The initial support includes:
 - MMC
 - eMMC
 - I2C
 - FEC
 - Serial console

Signed-off-by: Darren Huang <darren.huang@advantech.com.tw>
Signed-off-by: Kevin12.Chen <Kevin12.Chen@advantech.com.tw>
Signed-off-by: Phill.Liu <Phill.Liu@advantech.com.tw>
Signed-off-by: Tim Liang <tim.liang@advantech.com.tw>
Signed-off-by: wei.zeng <wei.zeng@advantech.com.cn>
Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Cc: uboot-imx <uboot-imx@nxp.com>
Cc: Peng Fan (OSS) <peng.fan@oss.nxp.com>
diff --git a/board/advantech/imx8mp_rsb3720a1/MAINTAINERS b/board/advantech/imx8mp_rsb3720a1/MAINTAINERS
new file mode 100644
index 0000000..bc967af
--- /dev/null
+++ b/board/advantech/imx8mp_rsb3720a1/MAINTAINERS
@@ -0,0 +1,7 @@
+i.MX8MP RSB3720 BOARD
+M:	Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
+S:	Maintained
+F:	board/advantech/imx8mp_rsb3720a1/
+F:	include/configs/imx8mp_rsb3720a1.h
+F:	configs/imx8mp_rsb3720a1_4G_defconfig
+F:	configs/imx8mp_rsb3720a1_6G_defconfig