dm: x86: Add a northbridge uclass

Add a uclass for the northbridge / SDRAM controller found on some older
Intel chipsets.

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

arch/x86/lib/Makefile

@@ -19,6 +19,7 @@ obj-y	+= lpc-uclass.o
 obj-y	+= mpspec.o
 obj-$(CONFIG_ENABLE_MRC_CACHE) += mrccache.o
 obj-y += cmd_mtrr.o
+obj-y	+= northbridge-uclass.o
 obj-$(CONFIG_I8259_PIC) += i8259.o
 obj-$(CONFIG_I8254_TIMER) += i8254.o
 ifndef CONFIG_DM_PCI

arch/x86/lib/northbridge-uclass.c

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2015 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <dm/root.h>
+
+UCLASS_DRIVER(northbridge) = {
+	.id		= UCLASS_NORTHBRIDGE,
+	.name		= "northbridge",
+};

include/dm/uclass-id.h

@@ -46,6 +46,7 @@ enum uclass_id {
 	UCLASS_MMC,		/* SD / MMC card or chip */
 	UCLASS_MOD_EXP,		/* RSA Mod Exp device */
 	UCLASS_MTD,		/* Memory Technology Device (MTD) device */
+	UCLASS_NORTHBRIDGE,	/* Intel Northbridge / SDRAM controller */
 	UCLASS_PANEL,		/* Display panel, such as an LCD */
 	UCLASS_PANEL_BACKLIGHT,	/* Backlight controller for panel */
 	UCLASS_PCH,		/* x86 platform controller hub */