feat(smccc): add vendor-specific el3 service

Add support for vendor-specific el3 service. SMCCC 1.5 introduces
support for vendor-specific EL3 monitor calls.

SMCCC Documentation reference:
https://developer.arm.com/docs/den0028/latest

Change-Id: Id8bc43842eecdb7a8a2ec7f31a631e88fe4fe0b4
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
diff --git a/include/services/ven_el3_svc.h b/include/services/ven_el3_svc.h
new file mode 100644
index 0000000..505e4fd
--- /dev/null
+++ b/include/services/ven_el3_svc.h
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2024, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef VEN_EL3_SVC_H
+#define VEN_EL3_SVC_H
+
+/*
+ * Function Identifier value ranges for Vendor-Specific
+ * EL3 Monitor Service Calls.
+ */
+/* VEN_EL3_SMC_32		0x87000000U */
+/* VEN_EL3_SMC_64		0xC7000000U */
+
+
+/* Function Identifier values of general queries */
+#define VEN_EL3_SVC_UID		0x8700ff01
+/*				0x8700ff02 is reserved */
+#define VEN_EL3_SVC_VERSION	0x8700ff03
+
+#define VEN_EL3_SVC_VERSION_MAJOR	1
+#define VEN_EL3_SVC_VERSION_MINOR	0
+
+#endif /* VEN_EL3_SVC_H */