Add serializer service for protobuf

Implements a serializer service for protobuf using nanopb. Adds external
component to fetch nanopb.

Change-Id: I31464be0e38d78bdf543e9f30bd51218e935dc9d
Signed-off-by: Julian Hall <julian.hall@arm.com>
diff --git a/components/service/common/serializer/protobuf/component.cmake b/components/service/common/serializer/protobuf/component.cmake
new file mode 100644
index 0000000..b9f8d97
--- /dev/null
+++ b/components/service/common/serializer/protobuf/component.cmake
@@ -0,0 +1,13 @@
+#-------------------------------------------------------------------------------
+# Copyright (c) 2020, Arm Limited and Contributors. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+#-------------------------------------------------------------------------------
+if (NOT DEFINED TGT)
+	message(FATAL_ERROR "mandatory parameter TGT is not defined.")
+endif()
+
+target_sources(${TGT} PRIVATE
+	"${CMAKE_CURRENT_LIST_DIR}/pb_helper.c"
+	)