feat(rme): add RMM dispatcher (RMMD)

This patch introduces the RMM dispatcher into BL31. This
will be the mechanism that will enable communication to
take place between the Realm and non-secure world. Currently
gives the capability for granules to be
transitioned from non-secure type to realm and vice versa.

Signed-off-by: Zelalem Aweke <zelalem.aweke@arm.com>
Signed-off-by: Subhasish Ghosh <subhasish.ghosh@arm.com>
Change-Id: I1fdc99a4bdd42bc14911aa0c6954b131de309511
diff --git a/services/std_svc/rmmd/rmmd_initial_context.h b/services/std_svc/rmmd/rmmd_initial_context.h
new file mode 100644
index 0000000..d7a743d
--- /dev/null
+++ b/services/std_svc/rmmd/rmmd_initial_context.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2021, Arm Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef RMMD_INITIAL_CONTEXT_H
+#define RMMD_INITIAL_CONTEXT_H
+
+#include <arch.h>
+
+/*
+ * SPSR_EL2
+ *   M=0x9 (0b1001 EL2h)
+ *   M[4]=0
+ *   DAIF=0xF Exceptions masked on entry.
+ *   BTYPE=0  BTI not yet supported.
+ *   SSBS=0   Not yet supported.
+ *   IL=0     Not an illegal exception return.
+ *   SS=0     Not single stepping.
+ *   PAN=1    RMM shouldn't access realm memory.
+ *   UAO=0
+ *   DIT=0
+ *   TCO=0
+ *   NZCV=0
+ */
+#define REALM_SPSR_EL2		(					\
+					SPSR_M_EL2H			| \
+					(0xF << SPSR_DAIF_SHIFT)	| \
+					SPSR_PAN_BIT			\
+				)
+
+#endif /* RMMD_INITIAL_CONTEXT_H */