drivers: nand: brcmnand: add initial support

The driver brcmnand come from linux kernel 4.18.
Only SoC bcm6838 and bcm6858 are supported.

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
diff --git a/drivers/mtd/nand/raw/brcmnand/brcmnand.h b/drivers/mtd/nand/raw/brcmnand/brcmnand.h
new file mode 100644
index 0000000..6946a62
--- /dev/null
+++ b/drivers/mtd/nand/raw/brcmnand/brcmnand.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#ifndef __BRCMNAND_H__
+#define __BRCMNAND_H__
+
+#include <linux/types.h>
+#include <linux/io.h>
+
+struct brcmnand_soc {
+	bool (*ctlrdy_ack)(struct brcmnand_soc *soc);
+	void (*ctlrdy_set_enabled)(struct brcmnand_soc *soc, bool en);
+	void (*prepare_data_bus)(struct brcmnand_soc *soc, bool prepare,
+				 bool is_param);
+	void *ctrl;
+};
+
+static inline void brcmnand_soc_data_bus_prepare(struct brcmnand_soc *soc,
+						 bool is_param)
+{
+	if (soc && soc->prepare_data_bus)
+		soc->prepare_data_bus(soc, true, is_param);
+}
+
+static inline void brcmnand_soc_data_bus_unprepare(struct brcmnand_soc *soc,
+						   bool is_param)
+{
+	if (soc && soc->prepare_data_bus)
+		soc->prepare_data_bus(soc, false, is_param);
+}
+
+static inline u32 brcmnand_readl(void __iomem *addr)
+{
+	/*
+	 * MIPS endianness is configured by boot strap, which also reverses all
+	 * bus endianness (i.e., big-endian CPU + big endian bus ==> native
+	 * endian I/O).
+	 *
+	 * Other architectures (e.g., ARM) either do not support big endian, or
+	 * else leave I/O in little endian mode.
+	 */
+	if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_SYS_BIG_ENDIAN))
+		return __raw_readl(addr);
+	else
+		return readl_relaxed(addr);
+}
+
+static inline void brcmnand_writel(u32 val, void __iomem *addr)
+{
+	/* See brcmnand_readl() comments */
+	if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_SYS_BIG_ENDIAN))
+		__raw_writel(val, addr);
+	else
+		writel_relaxed(val, addr);
+}
+
+int brcmnand_probe(struct udevice *dev, struct brcmnand_soc *soc);
+int brcmnand_remove(struct udevice *dev);
+
+#ifndef __UBOOT__
+extern const struct dev_pm_ops brcmnand_pm_ops;
+#endif /* __UBOOT__ */
+
+#endif /* __BRCMNAND_H__ */