bsh: imx8mn-smm-s2/pro: Add iMX8MN BSH SMM S2 boards

Introduce BSH SystemMaster (SMM) S2 board family, which consists of:
iMX8MN SMM S2 and iMX8MN SMM S2 PRO boards.

Add support for iMX8MN BSH SMM S2 board:

- 256 MiB DDR3 RAM
- 512MiB Nand
- USBOTG1 peripheral - fastboot.
- 100Mbit Ethernet

Add support for iMX8MN BSH SMM S2 PRO board:

- 512 MiB DDR3 RAM
- 8 GiB eMMC
- USBOTG1 peripheral - fastboot.
- 100Mbit Ethernet

Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
diff --git a/board/bsh/imx8mn_smm_s2/MAINTAINERS b/board/bsh/imx8mn_smm_s2/MAINTAINERS
new file mode 100644
index 0000000..1de816c
--- /dev/null
+++ b/board/bsh/imx8mn_smm_s2/MAINTAINERS
@@ -0,0 +1,8 @@
+ARM i.MX8MN BSH SMM S2 BOARDS
+M:	Ariel D'Alessandro <ariel.dalessandro@collabora.com>
+M:	Michael Trimarchi <michael@amarulasolutions.com>
+S:	Maintained
+F:	arch/arm/dts/imx8mn-bsh-smm-s2*
+F:	board/bsh/imx8mn_smm_s2/
+F:	configs/imx8mn_bsh_smm_s2*
+F:	include/configs/imx8mn_bsh_smm_s2*