x86: ivybridge: Add a driver for the bd82x6x northbridge

Add a driver with an empty probe function where we can move init code in
follow-on patches.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/ivybridge/early_init.c

@@ -8,6 +8,7 @@
  */
 
 #include <common.h>
+#include <dm.h>
 #include <asm/io.h>
 #include <asm/pci.h>
 #include <asm/arch/pch.h>
@@ -145,3 +146,20 @@ void sandybridge_early_init(int chipset_type)
 
 	sandybridge_setup_graphics(pch_dev, video_dev);
 }
+
+static int bd82x6x_northbridge_probe(struct udevice *dev)
+{
+	return 0;
+}
+
+static const struct udevice_id bd82x6x_northbridge_ids[] = {
+	{ .compatible = "intel,bd82x6x-northbridge" },
+	{ }
+};
+
+U_BOOT_DRIVER(bd82x6x_northbridge_drv) = {
+	.name		= "bd82x6x_northbridge",
+	.id		= UCLASS_NORTHBRIDGE,
+	.of_match	= bd82x6x_northbridge_ids,
+	.probe		= bd82x6x_northbridge_probe,
+};

arch/x86/dts/chromebook_link.dts

@@ -166,6 +166,13 @@
 		ranges = <0x02000000 0x0 0xe0000000 0xe0000000 0 0x10000000
 			0x42000000 0x0 0xd0000000 0xd0000000 0 0x10000000
 			0x01000000 0x0 0x1000 0x1000 0 0xefff>;
+
+		northbridge@0,0 {
+			reg = <0x00000000 0 0 0 0>;
+			compatible = "intel,bd82x6x-northbridge";
+			u-boot,dm-pre-reloc;
+		};
+
 		sata {
 			compatible = "intel,pantherpoint-ahci";
 			intel,sata-mode = "ahci";