debugfs: add 9p device interface

The 9p interface provides abstraction layers allowing the software
that uses devices to be independent from the hardware.

This patch provides a file system abstraction to link drivers to their
devices and propose a common interface to expose driver operations to
higher layers. This file system can be used to access and configure a
device by doing read/write operations.

Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: Ia9662393baf489855dc0c8f389fe4a0afbc9c255
diff --git a/lib/debugfs/devc.c b/lib/debugfs/devc.c
new file mode 100644
index 0000000..13c553d
--- /dev/null
+++ b/lib/debugfs/devc.c
@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2019, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+typedef struct dev dev_t;
+
+extern dev_t rootdevtab;
+
+dev_t *const devtab[] = {
+	&rootdevtab,
+	0
+};
+
+void devlink(void)
+{
+}