board/seco: Add mx6q-uq7 basic board support

Add basic SECO MX6Q/uQ7 board support (Ethernet, UART, SD are supported).
It also adds a Kconfig skeleton to later add more SECO board (supporting
SoC and board variants).

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
diff --git a/board/seco/common/mx6.h b/board/seco/common/mx6.h
new file mode 100644
index 0000000..a05db67
--- /dev/null
+++ b/board/seco/common/mx6.h
@@ -0,0 +1,9 @@
+#ifndef __SECO_COMMON_MX6_H
+#define __SECO_COMMON_MX6_H
+
+void seco_mx6_setup_uart_iomux(void);
+void seco_mx6_setup_enet_iomux(void);
+int seco_mx6_rgmii_rework(struct phy_device *phydev);
+void seco_mx6_setup_usdhc_iomux(int id);
+
+#endif /* __SECO_COMMON_MX6_H */