Index: sys/arm64/arm64/intr_machdep.c
===================================================================
--- sys/arm64/arm64/intr_machdep.c
+++ sys/arm64/arm64/intr_machdep.c
@@ -446,6 +446,13 @@
 	critical_exit();
 }
 
+void
+arm_unmask_irq(u_int irq)
+{
+
+	PIC_UNMASK(root_pic, irq);
+}
+
 #ifdef SMP
 void
 arm_setup_ipihandler(driver_filter_t *filt, u_int ipi)
Index: sys/arm64/arm64/nexus.c
===================================================================
--- sys/arm64/arm64/nexus.c
+++ sys/arm64/arm64/nexus.c
@@ -112,6 +112,7 @@
 static int nexus_setup_intr(device_t dev, device_t child, struct resource *res,
     int flags, driver_filter_t *filt, driver_intr_t *intr, void *arg, void **cookiep);
 static int nexus_teardown_intr(device_t, device_t, struct resource *, void *);
+static int nexus_unmask_intr(device_t, device_t, struct resource *);
 
 #ifdef FDT
 static int nexus_ofw_map_intr(device_t dev, device_t child, phandle_t iparent,
@@ -130,6 +131,7 @@
 	DEVMETHOD(bus_deactivate_resource,	nexus_deactivate_resource),
 	DEVMETHOD(bus_setup_intr,	nexus_setup_intr),
 	DEVMETHOD(bus_teardown_intr,	nexus_teardown_intr),
+	DEVMETHOD(bus_unmask_intr,		nexus_unmask_intr),
 
 	{ 0, 0 }
 };
@@ -288,6 +290,18 @@
 }
 
 static int
+nexus_unmask_intr(device_t dev, device_t child, struct resource *res)
+{
+
+	if (res == NULL)
+		return (EINVAL);
+
+	arm_unmask_irq(rman_get_start(res));
+
+	return (0);
+}
+
+static int
 nexus_teardown_intr(device_t dev, device_t child, struct resource *r, void *ih)
 {
 
Index: sys/dev/fdt/simplebus.c
===================================================================
--- sys/dev/fdt/simplebus.c
+++ sys/dev/fdt/simplebus.c
@@ -85,6 +85,7 @@
 	DEVMETHOD(bus_read_ivar,	bus_generic_read_ivar),
 	DEVMETHOD(bus_write_ivar,	bus_generic_write_ivar),
 	DEVMETHOD(bus_setup_intr,	bus_generic_setup_intr),
+	DEVMETHOD(bus_unmask_intr,	bus_generic_unmask_intr),
 	DEVMETHOD(bus_teardown_intr,	bus_generic_teardown_intr),
 	DEVMETHOD(bus_alloc_resource,	simplebus_alloc_resource),
 	DEVMETHOD(bus_release_resource,	bus_generic_release_resource),
Index: sys/kern/bus_if.m
===================================================================
--- sys/kern/bus_if.m
+++ sys/kern/bus_if.m
@@ -390,6 +390,21 @@
 };
 
 /**
+ * @brief Unmask an interrupt handler
+ *
+ * This method is used to mask the previously set up interrupt.
+ * 
+ * @param _dev		the parent device of @p _child
+ * @param _child	the device which allocated the resource
+ * @param _irq		the resource representing the interrupt
+ */
+METHOD int unmask_intr {
+	device_t	_dev;
+	device_t	_child;
+	struct resource *_irq;
+};
+
+/**
  * @brief Uninstall an interrupt handler
  *
  * This method is used to disassociate an interrupt handler function
Index: sys/kern/subr_bus.c
===================================================================
--- sys/kern/subr_bus.c
+++ sys/kern/subr_bus.c
@@ -3926,6 +3926,23 @@
 }
 
 /**
+ * @brief Helper function for implementing BUS_UNMASK_INTR().
+ *
+ * This simple implementation of BUS_UNMASK_INTR() simply calls the
+ * BUS_UNMASK_INTR() method of the parent of @p dev.
+ */
+int
+bus_generic_unmask_intr(device_t dev, device_t child, struct resource *irq)
+{
+
+	/* Propagate up the bus hierarchy until someone handles it. */
+	if (dev->parent)
+		return (BUS_UNMASK_INTR(dev->parent, child, irq));
+
+	return (EINVAL);
+}
+
+/**
  * @brief Helper function for implementing BUS_TEARDOWN_INTR().
  *
  * This simple implementation of BUS_TEARDOWN_INTR() simply calls the
@@ -4379,6 +4396,27 @@
 }
 
 /**
+ * @brief Wrapper function for BUS_UNMASK_INTR().
+ *
+ * This function simply calls the BUS_UNMASK_INTR() method of the
+ * parent of @p dev.
+ */
+int
+bus_unmask_intr(device_t dev, struct resource *r)
+{
+	int error;
+
+	if (dev->parent == NULL)
+		return (EINVAL);
+
+	error = BUS_UNMASK_INTR(dev->parent, dev, r);
+	if (error != 0)
+		return (error);
+
+	return (0);
+}
+
+/**
  * @brief Wrapper function for BUS_TEARDOWN_INTR().
  *
  * This function simply calls the BUS_TEARDOWN_INTR() method of the
Index: sys/sys/bus.h
===================================================================
--- sys/sys/bus.h
+++ sys/sys/bus.h
@@ -402,6 +402,8 @@
 			       struct resource *irq, int flags,
 			       driver_filter_t *filter, driver_intr_t *intr, 
 			       void *arg, void **cookiep);
+int	bus_generic_unmask_intr(device_t dev, device_t child,
+			       struct resource *irq);
 
 struct resource *
 	bus_generic_rl_alloc_resource (device_t, device_t, int, int *,
@@ -456,6 +458,7 @@
 		       driver_filter_t filter, driver_intr_t handler, 
 		       void *arg, void **cookiep);
 int	bus_teardown_intr(device_t dev, struct resource *r, void *cookie);
+int	bus_unmask_intr(device_t dev, struct resource *r);
 int	bus_bind_intr(device_t dev, struct resource *r, int cpu);
 int	bus_describe_intr(device_t dev, struct resource *irq, void *cookie,
 			  const char *fmt, ...);