powerpc/pci: Add pci_find_controller_for_domain()

Add a helper to find the pci_controller structure based on the domain
number / phb id.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Reviewed-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index cbdf13d..60f20c2 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -351,6 +351,17 @@ struct pci_controller* pci_find_hose_for_OF_device(struct device_node* node)
 	return NULL;
 }
 
+struct pci_controller *pci_find_controller_for_domain(int domain_nr)
+{
+	struct pci_controller *hose;
+
+	list_for_each_entry(hose, &hose_list, list_node)
+		if (hose->global_number == domain_nr)
+			return hose;
+
+	return NULL;
+}
+
 /*
  * Reads the interrupt pin to determine if interrupt is use by card.
  * If the interrupt is used, then gets the interrupt line from the