feat(fvp): enable external SP images in BL2 config

Currently the list of SP UUIDs loaded by BL2 is hardcoded in the DT.
This is a problem when building a system with other SPs (e.g. from
Trusted Services). This commit implements a workaround to enable adding
SP UUIDs to the list at build time.

Signed-off-by: Balint Dobszay <balint.dobszay@arm.com>
Change-Id: Iff85d3778596d23d777dec458f131bd7a8647031

Makefile

@@ -525,6 +525,10 @@ ifneq (${SPD},none)
         ifeq ($(TS_SP_FW_CONFIG),1)
             DTC_CPPFLAGS	+=	-DTS_SP_FW_CONFIG
         endif
+
+        ifneq ($(ARM_BL2_SP_LIST_DTS),)
+            DTC_CPPFLAGS += -DARM_BL2_SP_LIST_DTS=$(ARM_BL2_SP_LIST_DTS)
+        endif
     else
         # All other SPDs in spd directory
         SPD_DIR := spd

docs/plat/arm/arm-build-options.rst

@@ -100,6 +100,9 @@ Arm Platform Build Options
 -  ``ARM_SPMC_MANIFEST_DTS`` : path to an alternate manifest file used as the
    SPMC Core manifest. Valid when ``SPD=spmd`` is selected.
 
+-  ``ARM_BL2_SP_LIST_DTS``: Path to DTS file snippet to override the hardcoded
+   SP nodes in tb_fw_config.
+
 -  ``OPTEE_SP_FW_CONFIG``: DTC build flag to include OP-TEE as SP in tb_fw_config
    device tree. This flag is defined only when ``ARM_SPMC_MANIFEST_DTS`` manifest
    file name contains pattern optee_sp.

plat/arm/board/fvp/fdts/fvp_tb_fw_config.dts

@@ -4,6 +4,8 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
+#include <lib/libc/cdefs.h>
+
 /dts-v1/;
 
 / {
@@ -74,6 +76,10 @@
 
 	secure-partitions {
 		compatible = "arm,sp";
+
+#ifdef ARM_BL2_SP_LIST_DTS
+	#include __XSTRING(ARM_BL2_SP_LIST_DTS)
+#else
 #ifdef OPTEE_SP_FW_CONFIG
 		op-tee {
 			uuid = "486178e0-e7f8-11e3-bc5e-0002a5d5c51b";
@@ -104,6 +110,7 @@
 			owner = "Plat";
 		};
 #endif
+#endif /* ARM_BL2_SP_LIST_DTS */
 	};
 
 #if COT_DESC_IN_DTB