diff --git a/protocols/rpc/common/packed-c/encoding.h b/protocols/rpc/common/packed-c/encoding.h
new file mode 100644
index 0000000..cd7093c
--- /dev/null
+++ b/protocols/rpc/common/packed-c/encoding.h
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2020-2021, Arm Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef PROTOCOLS_RPC_COMMON_ENCODING_H
+#define PROTOCOLS_RPC_COMMON_ENCODING_H
+
+/*
+ * Encodings used for parameter serialization.
+ */
+enum
+{
+    /*
+     * Packed-c encoding.  A lightweight serialization scheme with
+     * C language definition files.
+     */
+    TS_RPC_ENCODING_PACKED_C        =  0,
+
+    /*
+     * Protocol Buffers serialization scheme with language independent
+     * definition files.  Supports client code generation using definition
+     * files.
+     */
+    TS_RPC_ENCODING_PROTOBUF        =  1,
+
+    /*
+     * The limit of known encodings.  As new encodings are added,
+     * the limit value should be allowed to increase.  An RPC interface
+     * that was built before a new encoding was added should safely
+     * reject an unsupported encoding.
+     */
+    TS_RPC_ENCODING_LIMIT
+};
+
+#endif /* PROTOCOLS_RPC_COMMON_ENCODING_H */