drivers/mtd: Add W25N SPI NAND flash driver

Add MTD driver for Winbond W25N series SPI NAND flash.

Currently supports W25N01GV (1Gbit/128MB).

Features:
- Standard SPI interface with configurable frequency (up to 104 MHz)
- Hardware ECC enabled by default
- Block erase with sleep-based wait (releases SPI bus)
- Page read/write with busy-wait for fast operations

Limitations:
- No bad block management (BBM). Factory bad blocks and runtime bad
  blocks are not tracked.
- No bad block table (BBT) scanning at initialization.
- No Quad SPI support (standard SPI only).
- No access to spare area (64 bytes/page) or OTP region.

Tested using:
- Board with STM32H743
- W25N01GV on SPI at 96 MHz with DMA enabled
- Flash mounted using littlefs
- Tested using sdbench:
  - Sequential write speed of 1760 KB/s
  - Sequential read speed of 4900 KB/s

Signed-off-by: Julian Oes <julian@oes.ch>

drivers/mtd/CMakeLists.txt

@@ -138,6 +138,10 @@ if(CONFIG_MTD)
     list(APPEND SRCS gd5f.c)
   endif()
 
+  if(CONFIG_MTD_W25N)
+    list(APPEND SRCS w25n.c)
+  endif()
+
   if(CONFIG_MTD_AT25)
     list(APPEND SRCS at25.c)
   endif()

drivers/mtd/Kconfig

@@ -1441,6 +1441,28 @@ config GD5F_SPIFREQUENCY
 
 endif # MTD_GD5F
 
+config MTD_W25N
+	bool "SPI-based W25N NAND FLASH"
+	default n
+	select SPI
+	---help---
+		Enable support for Winbond W25N SPI NAND flash.
+		Currently only W25N01GV (1Gbit/128MB) is supported.
+
+if MTD_W25N
+
+config W25N_SPIMODE
+	int "W25N SPI Mode"
+	default 0
+
+config W25N_SPIFREQUENCY
+	int "W25N SPI Frequency"
+	default 20000000
+	---help---
+		W25N01GV supports up to 104 MHz.
+
+endif # MTD_W25N
+
 config MTD_DHARA
 	bool "MTD Nandflash use dhara map"
 	default n

drivers/mtd/Make.defs

@@ -141,6 +141,10 @@ ifeq ($(CONFIG_MTD_GD5F),y)
 CSRCS += gd5f.c
 endif
 
+ifeq ($(CONFIG_MTD_W25N),y)
+CSRCS += w25n.c
+endif
+
 ifeq ($(CONFIG_MTD_AT25),y)
 CSRCS += at25.c
 endif

include/nuttx/mtd/mtd.h

@@ -616,7 +616,7 @@ FAR struct mtd_dev_s *sst39vf_initialize(void);
  *
  * Description:
  *   Initializes the driver for SPI-based W25x16, x32, and x64 and W25q16,
- *   q32, q64, and q128 FLASH
+ *   q32, q64, and q128 NOR FLASH
  *
  ****************************************************************************/
 
@@ -655,6 +655,17 @@ FAR struct mtd_dev_s *gd55_initialize(FAR struct qspi_dev_s *dev,
 FAR struct mtd_dev_s *gd5f_initialize(FAR struct spi_dev_s *dev,
                                       uint32_t spi_devid);
 
+/****************************************************************************
+ * Name: w25n_initialize
+ *
+ * Description:
+ *   Initializes the driver for SPI-based W25N NAND FLASH
+ *
+ ****************************************************************************/
+
+FAR struct mtd_dev_s *w25n_initialize(FAR struct spi_dev_s *dev,
+                                      uint32_t spi_devid);
+
 /****************************************************************************
  * Name: s25fl1_initialize
  *