Index: head/sys/kern/subr_bus.c
===================================================================
--- head/sys/kern/subr_bus.c
+++ head/sys/kern/subr_bus.c
@@ -285,6 +285,7 @@
 device_sysctl_init(device_t dev)
 {
 	devclass_t dc = dev->devclass;
+	int domain;
 
 	if (dev->sysctl_tree != NULL)
 		return;
@@ -314,6 +315,10 @@
 	    OID_AUTO, "%parent", CTLTYPE_STRING | CTLFLAG_RD,
 	    dev, DEVICE_SYSCTL_PARENT, device_sysctl_handler, "A",
 	    "parent device");
+	if (bus_get_domain(dev, &domain) == 0)
+		SYSCTL_ADD_INT(&dev->sysctl_ctx,
+		    SYSCTL_CHILDREN(dev->sysctl_tree), OID_AUTO, "%domain",
+		    CTLFLAG_RD, NULL, domain, "NUMA domain");
 }
 
 static void
@@ -4542,6 +4547,18 @@
 	return (BUS_GET_DMA_TAG(parent, dev));
 }
 
+/**
+ * @brief Wrapper function for BUS_GET_DOMAIN().
+ *
+ * This function simply calls the BUS_GET_DOMAIN() method of the
+ * parent of @p dev.
+ */
+int
+bus_get_domain(device_t dev, int *domain)
+{
+	return (BUS_GET_DOMAIN(device_get_parent(dev), dev, domain));
+}
+
 /* Resume all devices and then notify userland that we're up again. */
 static int
 root_resume(device_t dev)
Index: head/sys/sys/bus.h
===================================================================
--- head/sys/sys/bus.h
+++ head/sys/sys/bus.h
@@ -392,6 +392,7 @@
 int	bus_deactivate_resource(device_t dev, int type, int rid,
 				struct resource *r);
 bus_dma_tag_t bus_get_dma_tag(device_t dev);
+int	bus_get_domain(device_t dev, int *domain);
 int	bus_release_resource(device_t dev, int type, int rid,
 			     struct resource *r);
 int	bus_free_resource(device_t dev, int type, struct resource *r);