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/arch/arm/dts/imx8mn-bsh-smm-s2-u-boot.dtsi b/arch/arm/dts/imx8mn-bsh-smm-s2-u-boot.dtsi
new file mode 100644
index 0000000..bd4da7d
--- /dev/null
+++ b/arch/arm/dts/imx8mn-bsh-smm-s2-u-boot.dtsi
@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2021 Collabora Ltd.
+ * Copyright 2021 BSH Hausgeraete GmbH
+ */
+
+#include "imx8mn-bsh-smm-s2-u-boot-common.dtsi"
+
+&pinctrl_gpmi_nand {
+	u-boot,dm-spl;
+};
+
+&gpmi {
+	u-boot,dm-spl;
+};