Add media top-level directory for storage medium access components

Introduces the top-level media directory for components concerned
with accessing storage media using well-known formats. Reuses
external source code from TF-A where possible.

Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: I5fa2cb24aa33f019df5108e80ccd78f0170e4c0b
diff --git a/components/media/volume/image_source/image_source.c b/components/media/volume/image_source/image_source.c
new file mode 100644
index 0000000..8dcbac4
--- /dev/null
+++ b/components/media/volume/image_source/image_source.c
@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+#include <plat/common/platform.h>
+
+int plat_get_image_source(
+	unsigned int image_id,
+	uintptr_t *dev_handle,
+	uintptr_t *image_spec)
+{
+	/* Needs to allow a TS factory method to define the image source */
+	(void)image_id;
+	*dev_handle = (uintptr_t)NULL;
+	*image_spec = (uintptr_t)NULL;
+	return -1;
+}
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