Documentation: Destage TEE subsystem documentation

Add a separate documentation directory for TEE subsystem since it is a
standalone subsystem which already offers devices consumed by multiple
different subsystem drivers.

Split overall TEE subsystem documentation modularly where:
- The userspace API has been moved to Documentation/userspace-api/tee.rst.
- The driver API has been moved to Documentation/driver-api/tee.rst.
- The first module covers the overview of TEE subsystem.
- The further modules are dedicated to different TEE implementations like:
  - OP-TEE
  - AMD-TEE
  - and so on for future TEE implementation support.

Acked-by: Rijo Thomas <Rijo-john.Thomas@amd.com>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20231128072352.866859-1-sumit.garg@linaro.org

1 files changed, 22 insertions, 0 deletions

diff --git a/Documentation/tee/tee.rst b/Documentation/tee/tee.rst
new file mode 100644
index 000000000000..fd9f8c4ff63d
--- /dev/null
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+.. SPDX-License-Identifier: GPL-2.0
+
+===================================
+TEE (Trusted Execution Environment)
+===================================
+
+This document describes the TEE subsystem in Linux.
+
+Overview
+========
+
+A TEE is a trusted OS running in some secure environment, for example,
+TrustZone on ARM CPUs, or a separate secure co-processor etc. A TEE driver
+handles the details needed to communicate with the TEE.
+
+This subsystem deals with:
+
+- Registration of TEE drivers
+
+- Managing shared memory between Linux and the TEE
+
+- Providing a generic API to the TEE