Demonstrate model for routing IRQs to EL3

This patch provides an option to specify a interrupt routing model
where non-secure interrupts (IRQs) are routed to EL3 instead of S-EL1.
When such an interrupt occurs, the TSPD arranges a return to
the normal world after saving any necessary context. The interrupt
routing model to route IRQs to EL3 is enabled only during STD SMC
processing. Thus the pre-emption of S-EL1 is disabled during Fast SMC
and Secure Interrupt processing.

A new build option TSPD_ROUTE_NS_INT_EL3 is introduced to change
the non secure interrupt target execution level to EL3.

Fixes ARM-software/tf-issues#225

Change-Id: Ia1e779fbbb6d627091e665c73fa6315637cfdd32
diff --git a/include/bl31/interrupt_mgmt.h b/include/bl31/interrupt_mgmt.h
index 3a2c00c..e07ddf8 100644
--- a/include/bl31/interrupt_mgmt.h
+++ b/include/bl31/interrupt_mgmt.h
@@ -63,7 +63,8 @@
 #define INTR_NS_VALID_RM0		0x0
 /* Routed to EL1/EL2 from NS and to EL3 from Secure */
 #define INTR_NS_VALID_RM1		0x1
-
+/* This is the default routing model */
+#define INTR_DEFAULT_RM		0x0
 
 /*******************************************************************************
  * Constants for the _individual_ routing model bits in the 'flags' field for
@@ -123,6 +124,8 @@
 					interrupt_type_handler_t handler,
 					uint32_t flags);
 interrupt_type_handler_t get_interrupt_type_handler(uint32_t interrupt_type);
+int disable_intr_rm_local(uint32_t type, uint32_t security_state);
+int enable_intr_rm_local(uint32_t type, uint32_t security_state);
 
 #endif /*__ASSEMBLY__*/
 #endif /* __INTERRUPT_MGMT_H__ */