add data handler interface

Transport mechanisms will implement data interfaces to handle copying
data from outside the IPMI packet.

Change-Id: I335f9d79cbc278959fffd7e47b00934a936a279d
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/data_handler.hpp b/data_handler.hpp
new file mode 100644
index 0000000..07101f7
--- /dev/null
+++ b/data_handler.hpp
@@ -0,0 +1,15 @@
+#pragma once
+
+namespace blobs
+{
+
+/**
+ * Each data transport mechanism must implement the DataInterface.
+ */
+class DataInterface
+{
+  public:
+    virtual ~DataInterface() = default;
+};
+
+} // namespace blobs