board/adi/ev-sc598-som: support SPI NAND

The long-term availability of eMMC is in question. Support a modified
EV-SC598-SOM where the SPI flash has been replaced with a NAND part that
is pin compatible to evaluate performance on the EV-SC598-SOM.

Define two devicetree overlays, for Linux and U-Boot, because the
register values are off by one. This will eventually get cleaned up as
part of a bigger effort to clean-up Linux and remove the U-Boot
devicetrees.

Signed-off-by: Philip Molloy <philip.molloy@analog.com>

Author: pamolloy

board/adi/ev-sc598-som/nand.cfg

@@ -0,0 +1,40 @@
+# Micron 8Gb (1GB) SPI NAND flash
+# Model: MT29F8G01ADAFD12-AAT:F
+# Datasheet: https://www.micron.com/content/dam/micron/global/secure/products/data-sheet/nand-flash/70-series/m70a-4-8gb-nand-spi-auto.pdf
+# Label: U4
+flash nand-1G {
+	pebsize = 256K
+	numpebs = 4096
+	minimum-io-unit-size = 4096
+	sub-page-size = 4096
+	vid-header-offset = 4096
+}
+
+image nand.img {
+	flash {}
+	flashtype = "nand-1G"
+
+	partition u-boot-spl {
+		image = "u-boot-spl.ldr"
+		size = 256K
+	}
+
+	partition u-boot {
+		image = "u-boot.ldr"
+		size = 768K
+	}
+
+	partition dtb {
+		image = "sc598-som-nand.dtb"
+		size = 256K
+	}
+
+	partition kernel {
+		image = "Image"
+		size = 32M
+	}
+
+	partition rootfs {
+		image = "rootfs.ubi"
+	}
+}

board/adi/ev-sc598-som/patches/linux/dts/adi/sc598-som-nand.dts

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2026 Analog Devices Incorporated
+ */
+
+/dts-v1/;
+
+#include "sc598-som-revE.dtsi"
+
+/ {
+  model = "ADI SC598-SOM with NAND";
+  compatible = "adi,sc598-som-nand", "adi,sc59x-64";
+};
+
+&spi2 {
+	/delete-node/ is25lp01g@0;
+
+	som_flash: spi-nand@0 {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "spi-nand";
+		reg = <0>;
+		spi-max-frequency = <25000000>;
+		spi-rx-bus-width = <4>;
+		spi-tx-bus-width = <4>;
+
+		partitions {
+			compatible = "fixed-partitions";
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			partition@0 {
+				label = "u-boot-spl";
+				reg = <0x0 0x40000>;
+			};
+
+			partition@40000 {
+				label = "u-boot";
+				reg = <0x40000 0xC0000>;
+			};
+
+			partition@100000 {
+				label = "dtb";
+				reg = <0x100000 0x40000>;
+			};
+
+			partition@140000 {
+				label = "kernel";
+				reg = <0x140000 0x2000000>;
+			};
+
+			partition@2140000 {
+				label = "rootfs";
+				reg = <0x2140000 0x3DEC0000>;
+			};
+		};
+	};
+};

board/adi/ev-sc598-som/patches/linux/nand.fragment

@@ -0,0 +1,2 @@
+CONFIG_MTD_SPI_NAND=y
+CONFIG_MTD_UBI=y

board/adi/ev-sc598-som/patches/uboot/dts/sc598-som-nand.dts

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2026 Analog Devices Incorporated
+ */
+
+/dts-v1/;
+
+#include "sc598-som-revE.dtsi"
+
+/ {
+  model = "ADI SC598-SOM with NAND";
+  compatible = "adi,sc598-som-nand", "adi,sc59x-64";
+};
+
+&spi2 {
+	/delete-node/ is25lp01g@1;
+
+	som_flash: spi-nand@1 {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "spi-nand";
+		reg = <1>;
+		spi-max-frequency = <25000000>;
+		spi-rx-bus-width = <4>;
+		spi-tx-bus-width = <4>;
+
+		partitions {
+			compatible = "fixed-partitions";
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			partition@0 {
+				label = "u-boot-spl";
+				reg = <0x0 0x40000>;
+			};
+
+			partition@40000 {
+				label = "u-boot";
+				reg = <0x40000 0xC0000>;
+			};
+
+			partition@100000 {
+				label = "dtb";
+				reg = <0x100000 0x40000>;
+			};
+
+			partition@140000 {
+				label = "kernel";
+				reg = <0x140000 0x2000000>;
+			};
+
+			partition@2140000 {
+				label = "rootfs";
+				reg = <0x2140000 0x3DEC0000>;
+			};
+		};
+	};
+};

board/adi/ev-sc598-som/patches/uboot/nand.fragment

@@ -0,0 +1,3 @@
+CONFIG_DEFAULT_DEVICE_TREE="sc598-som-nand"
+CONFIG_DM_MTD=y
+CONFIG_MTD_SPI_NAND=y

configs/adi_sc598_nand.fragment

@@ -0,0 +1,7 @@
+BR2_LINUX_KERNEL_INTREE_DTS_NAME="adi/sc598-som-nand"
+BR2_LINUX_KERNEL_CUSTOM_DTS_DIR="$(BR2_EXTERNAL)/board/adi/ev-sc598-som/patches/linux/dts/"
+BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES="$(BR2_EXTERNAL)/board/adi/ev-sc598-som/patches/linux/nand.fragment"
+BR2_TARGET_UBOOT_CUSTOM_DTS_PATH="$(BR2_EXTERNAL)/board/adi/ev-sc598-som/patches/uboot/dts/sc598-som-nand.dts"
+BR2_TARGET_UBOOT_CONFIG_FRAGMENT_FILES="$(BR2_EXTERNAL)/board/adi/ev-sc598-som/patches/uboot/nand.fragment"
+BR2_ROOTFS_POST_IMAGE_SCRIPT_ARGS="-c $(BR2_EXTERNAL)/board/adi/ev-sc598-som/nand.cfg"
+# BR2_TARGET_ROOTFS_EXT2 is not set