ram: renesas: Add Renesas R-Car Gen4 DBSC5 driver

Add Renesas R-Car Gen4 DBSC5 DRAM controller driver. This driver is currently
capable of bringing LPDDR5 DRAM on Renesas R-Car V4H Whitehawk board. Further
boards can be supported by supplying board specific DRAM configuration data
via dbsc5_get_board_data(). Support for R-Car V4M is not implemented, however
the driver is already mostly prepared to support this SoC.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
diff --git a/drivers/ram/renesas/dbsc5/dbsc5.c b/drivers/ram/renesas/dbsc5/dbsc5.c
new file mode 100644
index 0000000..d24b7c5
--- /dev/null
+++ b/drivers/ram/renesas/dbsc5/dbsc5.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2024 Renesas Electronics Corp.
+ */
+
+#include <asm/io.h>
+#include <dm.h>
+#include <dm/device-internal.h>
+#include <dm/lists.h>
+#include <errno.h>
+#include <linux/sizes.h>
+#include <ram.h>
+#include "dbsc5.h"
+
+static int renesas_dbsc5_probe(struct udevice *dev)
+{
+	struct udevice *pdev;
+	int ret;
+
+	ret = uclass_get_device_by_name(UCLASS_RAM, "dbsc5_dram", &pdev);
+	if (ret)
+		return ret;
+
+	ret = uclass_get_device_by_name(UCLASS_NOP, "dbsc5_qos", &pdev);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+int renesas_dbsc5_bind(struct udevice *dev)
+{
+	struct udevice *ramdev, *qosdev;
+	struct driver *ramdrv, *qosdrv;
+	int ret;
+
+	ramdrv = lists_driver_lookup_name("dbsc5_dram");
+	if (!ramdrv)
+		return -ENOENT;
+
+
+	qosdrv = lists_driver_lookup_name("dbsc5_qos");
+	if (!qosdrv)
+		return -ENOENT;
+
+	ret = device_bind_with_driver_data(dev, ramdrv, "dbsc5_dram",
+					   dev_get_driver_data(dev),
+					   dev_ofnode(dev), &ramdev);
+	if (ret)
+		return ret;
+
+	ret = device_bind_with_driver_data(dev, qosdrv, "dbsc5_qos", 0,
+					   dev_ofnode(dev), &qosdev);
+	if (ret)
+		device_unbind(ramdev);
+
+	return ret;
+}
+
+struct renesas_dbsc5_data r8a779g0_dbsc5_data = {
+	.clock_node = "renesas,r8a779g0-cpg-mssr",
+	.reset_node = "renesas,r8a779g0-rst"
+};
+
+static const struct udevice_id renesas_dbsc5_ids[] = {
+	{
+		.compatible = "renesas,r8a779g0-dbsc",
+		.data = (ulong)&r8a779g0_dbsc5_data
+	},
+	{ /* sentinel */ }
+};
+
+U_BOOT_DRIVER(renesas_dbsc5) = {
+	.name		= "dbsc5",
+	.id		= UCLASS_NOP,
+	.of_match	= renesas_dbsc5_ids,
+	.bind		= renesas_dbsc5_bind,
+	.probe		= renesas_dbsc5_probe,
+};