variants/common/arduino_flash_fs.dtsi: Add common FS config.

Provides a common file system configuration and partitions that
can just be included by overlays.

Signed-off-by: iabdalkader <i.abdalkader@gmail.com>

Author: iabdalkader

variants/common/arduino_flash_fs.dtsi

@@ -0,0 +1,111 @@
+/*
+ * Common filesystem configuration
+ *
+ * This overlay defines the following:
+ *
+ * 1- Common partition layout for 16MB flash:
+ * - mbr: 4KB @ 0x000000 (Master Boot Record - protected)
+ * - wlan: ~1020KB @ 0x001000 (Network certificates)
+ * - ota: 5MB @ 0x100000 (OTA updates)
+ * - kvs: 1MB @ 0x600000 (Key-Value Store)
+ * - storage: 7MB @ 0x700000 (User data)
+ *
+ * 2- fstab entries and flash-disk devices for:
+ * - /wlan: (FAT) - Network certificates partition
+ * - /ota: (FAT) - OTA update partition
+ * - /storage (LittleFS) - User data partition
+ *
+ * Usage in board overlay:
+ *
+ * #define FLASH_FILESYSTEM_NODE   flash_node
+ * #include "../common/arduino_flash_fs.dtsi"
+ *
+ * Replace flash_node with your board's flash node (e.g., at25sf128a).
+ */
+flash_partitions: &FLASH_FILESYSTEM_NODE {
+	/delete-node/ partitions;
+    partitions {
+    	compatible = "fixed-partitions";
+    	#address-cells = <1>;
+    	#size-cells = <1>;
+    
+    	mbr_partition: partition@0 {
+    		label = "mbr";
+    		reg = <0x000000 DT_SIZE_K(4)>;
+    	};
+    
+        /* Partition 1: Network certificates 1MB - 4KB (MBR reserved at 0x0) */
+    	wlan_partition: partition@1000 {
+    		label = "wlan";
+            reg = <0x001000 (DT_SIZE_M(1) - DT_SIZE_K(4))>;
+    	};
+    
+        /* Partition 2: OTA 5MB */
+    	ota_partition: partition@100000 {
+    		label = "ota";
+    		reg = <0x100000 DT_SIZE_M(5)>;
+    	};
+    
+        /* Partition 3: Provisioning KVStore 1MB */
+    	kvs_partition: partition@600000 {
+    		label = "kvs";
+    		reg = <0x600000 DT_SIZE_M(1)>;
+    	};
+    
+        /* Partition 4: User data 7MB */
+    	storage_partition: partition@700000 {
+    		label = "storage";
+    		reg = <0x700000 DT_SIZE_M(7)>;
+    	};
+    };
+};
+
+/ {
+	flash_disk0 {
+		status = "okay";
+		compatible = "zephyr,flash-disk";
+		partition = <&wlan_partition>;
+		disk-name = "wlan";
+		sector-size = <4096>;
+		cache-size = <4096>;
+	};
+
+	flash_disk1 {
+		status = "okay";
+		compatible = "zephyr,flash-disk";
+		partition = <&ota_partition>;
+		disk-name = "ota";
+		sector-size = <4096>;
+		cache-size = <4096>;
+	};
+
+	fstab {
+		compatible = "zephyr,fstab";
+
+		wlan_fs: wlan_fs {
+			compatible = "zephyr,fstab,fatfs";
+			automount;
+			disk-access;
+			mount-point = "/wlan:";
+		};
+
+		ota_fs: ota_fs {
+			compatible = "zephyr,fstab,fatfs";
+			automount;
+			disk-access;
+			mount-point = "/ota:";
+		};
+
+		storage_fs: storage_fs {
+			compatible = "zephyr,fstab,littlefs";
+			automount;
+			mount-point = "/storage";
+			partition = <&storage_partition>;
+			read-size = <16>;
+			prog-size = <4096>;
+			cache-size = <4096>;
+			lookahead-size = <32>;
+			block-cycles = <512>;
+		};
+	};
+};