Index: head/sys/kern/subr_intr.c
===================================================================
--- head/sys/kern/subr_intr.c
+++ head/sys/kern/subr_intr.c
@@ -98,6 +98,15 @@
 static void *irq_root_arg;
 static u_int irq_root_ipicount;
 
+struct intr_pic_child {
+	SLIST_ENTRY(intr_pic_child)	 pc_next;
+	struct intr_pic			*pc_pic;
+	intr_child_irq_filter_t		*pc_filter;
+	void				*pc_filter_arg;
+	uintptr_t			 pc_start;
+	uintptr_t			 pc_length;
+};
+
 /* Interrupt controller definition. */
 struct intr_pic {
 	SLIST_ENTRY(intr_pic)	pic_next;
@@ -106,6 +115,8 @@
 #define	FLAG_PIC	(1 << 0)
 #define	FLAG_MSI	(1 << 1)
 	u_int			pic_flags;
+	struct mtx		pic_child_lock;
+	SLIST_HEAD(, intr_pic_child) pic_children;
 };
 
 static struct mtx pic_list_lock;
@@ -323,6 +334,29 @@
 #endif
 }
 
+int
+intr_child_irq_handler(struct intr_pic *parent, uintptr_t irq)
+{
+	struct intr_pic_child *child;
+	bool found;
+
+	found = false;
+	mtx_lock_spin(&parent->pic_child_lock);
+	SLIST_FOREACH(child, &parent->pic_children, pc_next) {
+		if (child->pc_start <= irq &&
+		    irq < (child->pc_start + child->pc_length)) {
+			found = true;
+			break;
+		}
+	}
+	mtx_unlock_spin(&parent->pic_child_lock);
+
+	if (found)
+		return (child->pc_filter(child->pc_filter_arg, irq));
+
+	return (FILTER_STRAY);
+}
+
 /*
  *  interrupt controller dispatch function for interrupts. It should
  *  be called straight from the interrupt controller, when associated interrupt
@@ -892,6 +926,7 @@
 	}
 	pic->pic_xref = xref;
 	pic->pic_dev = dev;
+	mtx_init(&pic->pic_child_lock, "pic child lock", NULL, MTX_SPIN);
 	SLIST_INSERT_HEAD(&pic_list, pic, pic_next);
 	mtx_unlock(&pic_list_lock);
 
@@ -1001,6 +1036,44 @@
 	return (0);
 }
 
+/*
+ * Add a handler to manage a sub range of a parents interrupts.
+ */
+struct intr_pic *
+intr_pic_add_handler(device_t parent, struct intr_pic *pic,
+    intr_child_irq_filter_t *filter, void *arg, uintptr_t start,
+    uintptr_t length)
+{
+	struct intr_pic *parent_pic;
+	struct intr_pic_child *newchild;
+#ifdef INVARIANTS
+	struct intr_pic_child *child;
+#endif
+
+	parent_pic = pic_lookup(parent, 0);
+	if (parent_pic == NULL)
+		return (NULL);
+
+	newchild = malloc(sizeof(*newchild), M_INTRNG, M_WAITOK | M_ZERO);
+	newchild->pc_pic = pic;
+	newchild->pc_filter = filter;
+	newchild->pc_filter_arg = arg;
+	newchild->pc_start = start;
+	newchild->pc_length = length;
+
+	mtx_lock_spin(&parent_pic->pic_child_lock);
+#ifdef INVARIANTS
+	SLIST_FOREACH(child, &parent_pic->pic_children, pc_next) {
+		KASSERT(child->pc_pic != pic, ("%s: Adding a child PIC twice",
+		    __func__));
+	}
+#endif
+	SLIST_INSERT_HEAD(&parent_pic->pic_children, newchild, pc_next);
+	mtx_unlock_spin(&parent_pic->pic_child_lock);
+
+	return (pic);
+}
+
 int
 intr_map_irq(device_t dev, intptr_t xref, struct intr_map_data *data,
     u_int *irqp)
Index: head/sys/sys/intr.h
===================================================================
--- head/sys/sys/intr.h
+++ head/sys/sys/intr.h
@@ -74,6 +74,7 @@
 #else
 typedef int intr_irq_filter_t(void *arg);
 #endif
+typedef int intr_child_irq_filter_t(void *arg, uintptr_t irq);
 
 #define INTR_ISRC_NAMELEN	(MAXCOMLEN + 1)
 
@@ -81,6 +82,8 @@
 #define INTR_ISRCF_PPI		0x02	/* PPI interrupt */
 #define INTR_ISRCF_BOUND	0x04	/* bound to a CPU */
 
+struct intr_pic;
+
 /* Interrupt source definition. */
 struct intr_irqsrc {
 	device_t		isrc_dev;	/* where isrc is mapped */
@@ -113,6 +116,8 @@
 struct intr_pic *intr_pic_register(device_t, intptr_t);
 int intr_pic_deregister(device_t, intptr_t);
 int intr_pic_claim_root(device_t, intptr_t, intr_irq_filter_t *, void *, u_int);
+struct intr_pic *intr_pic_add_handler(device_t, struct intr_pic *,
+    intr_child_irq_filter_t *, void *, uintptr_t, uintptr_t);
 
 extern device_t intr_irq_root_dev;
 
@@ -127,6 +132,7 @@
 int intr_teardown_irq(device_t, struct resource *, void *);
 
 int intr_describe_irq(device_t, struct resource *, void *, const char *);
+int intr_child_irq_handler(struct intr_pic *, uintptr_t);
 
 /* MSI/MSI-X handling */
 int intr_msi_register(device_t, intptr_t);