ARMv8: Allow SiP service extensions on top of PSCI code

Allow PSCI layer to handle any SiP service functions added by
platform vendors. PSCI layer will look for SiP service function
in the SiP function table located in '._secure_svc_tbl_entries'
section if the SMC function identifier is not found in the PSCI
standard functions table. Use DECLARE_SECURE_SVC macro to declare
and add platform specific SiP service function.
This new section '._secure_svc_tbl_entries' is located next to
'._secure.text' section. Refer to arch/arm/cpu/armv8/u-boot.lds.

Signed-off-by: Chee Hong Ang <chee.hong.ang@intel.com>
diff --git a/arch/arm/include/asm/secure.h b/arch/arm/include/asm/secure.h
index d23044a..50582c9 100644
--- a/arch/arm/include/asm/secure.h
+++ b/arch/arm/include/asm/secure.h
@@ -6,6 +6,37 @@
 #define __secure __attribute__ ((section ("._secure.text")))
 #define __secure_data __attribute__ ((section ("._secure.data")))
 
+#ifndef __ASSEMBLY__
+
+typedef struct secure_svc_tbl {
+	u32	id;
+#ifdef CONFIG_ARMV8_PSCI
+	u8	pad[4];
+#endif
+	void	*func;
+} secure_svc_tbl_t;
+
+/*
+ * Macro to declare a SiP function service in '_secure_svc_tbl_entries' section
+ */
+#define DECLARE_SECURE_SVC(_name, _id, _fn) \
+	static const secure_svc_tbl_t __secure_svc_ ## _name \
+		__attribute__((used, section("._secure_svc_tbl_entries"))) \
+			 = { \
+				.id = _id, \
+				.func = _fn }
+
+#else
+
+#ifdef CONFIG_ARMV8_PSCI
+#define SECURE_SVC_TBL_OFFSET		16
+#else
+#define SECURE_SVC_TBL_OFFSET		8
+
+#endif
+
+#endif /* __ASSEMBLY__ */
+
 #if defined(CONFIG_ARMV7_SECURE_BASE) || defined(CONFIG_ARMV8_SECURE_BASE)
 /*
  * Warning, horror ahead.