v4.19.13 snapshot.
diff --git a/include/linux/root_dev.h b/include/linux/root_dev.h
new file mode 100644
index 0000000..bab671b
--- /dev/null
+++ b/include/linux/root_dev.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ROOT_DEV_H_
+#define _ROOT_DEV_H_
+
+#include <linux/major.h>
+#include <linux/types.h>
+#include <linux/kdev_t.h>
+
+enum {
+ Root_NFS = MKDEV(UNNAMED_MAJOR, 255),
+ Root_RAM0 = MKDEV(RAMDISK_MAJOR, 0),
+ Root_RAM1 = MKDEV(RAMDISK_MAJOR, 1),
+ Root_FD0 = MKDEV(FLOPPY_MAJOR, 0),
+ Root_HDA1 = MKDEV(IDE0_MAJOR, 1),
+ Root_HDA2 = MKDEV(IDE0_MAJOR, 2),
+ Root_SDA1 = MKDEV(SCSI_DISK0_MAJOR, 1),
+ Root_SDA2 = MKDEV(SCSI_DISK0_MAJOR, 2),
+ Root_HDC1 = MKDEV(IDE1_MAJOR, 1),
+ Root_SR0 = MKDEV(SCSI_CDROM_MAJOR, 0),
+};
+
+extern dev_t ROOT_DEV;
+
+#endif