Index: sys/dev/ofw/ofw_fdt.c
===================================================================
--- sys/dev/ofw/ofw_fdt.c
+++ sys/dev/ofw/ofw_fdt.c
@@ -107,11 +107,13 @@
 #define	FDT_FBSDVER_LEN	16
 #define	FDT_MODEL_LEN	80
 #define	FDT_COMPAT_LEN	255
+#define	FDT_SERIAL_LEN	32
 
 static void *fdtp = NULL;
 static char fdt_model[FDT_MODEL_LEN];
 static char fdt_compatible[FDT_COMPAT_LEN];
 static char fdt_fbsd_version[FDT_FBSDVER_LEN];
+static char fdt_serial[FDT_SERIAL_LEN];
 
 static int
 sysctl_handle_dtb(SYSCTL_HANDLER_ARGS)
@@ -143,6 +145,10 @@
 		SYSCTL_ADD_STRING(NULL, SYSCTL_STATIC_CHILDREN(_hw_fdt),
 		    OID_AUTO, "freebsd-version", CTLFLAG_RD, fdt_fbsd_version,
 		    FDT_FBSDVER_LEN, "FreeBSD DTS branding version");
+	if (fdt_serial[0] != '\0')
+		SYSCTL_ADD_STRING(NULL, SYSCTL_STATIC_CHILDREN(_hw_fdt),
+		    OID_AUTO, "serial-number", CTLFLAG_RD, fdt_serial,
+		    FDT_SERIAL_LEN, "Serial number");
 }
 SYSINIT(dtb_oid, SI_SUB_KMEM, SI_ORDER_ANY, sysctl_register_fdt_oid, NULL);
 
@@ -175,6 +181,11 @@
 		ofw_fdt_getprop(NULL, root, "freebsd,dts-version",
 		  fdt_fbsd_version, FDT_FBSDVER_LEN);
 	}
+	if ((len = ofw_fdt_getproplen(NULL, root, "serial-number")) > 0) {
+		bzero(fdt_serial, FDT_SERIAL_LEN);
+		ofw_fdt_getprop(NULL, root, "serial-number",
+		  fdt_serial, FDT_SERIAL_LEN);
+	}
 	return (0);
 }