Apply Arm Trademark Guidance

This project uses Arm trademarks throughout source files, documentation
and tests. As per the Arm trademark guidance [1], the first use of each
of these trademarks must be preceded by the Arm word trademark.

This rule can be met by referring the user to the Arm Trademarks list on
the Arm website in the top level documentation, which in the case of this
project is the README.md file. This is considered to be "first use"
within the project as whole, with no necessity to adopt "First Use" form
within individual files throughout the source tree.

[1] https://www.arm.com/company/policies/trademarks/guidelines-trademarks
[2] https://www.arm.com/company/policies/trademarks/arm-trademark-list

Change-Id: I6bf6bc81ac1d8eea286f0f7bf3b2e434a2e75c28
Signed-off-by: Sandrine Afsa <sandrine.afsa@arm.com>
diff --git a/README.md b/README.md
index c6e6677..39bf94e 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,19 @@
 
 Contributions are handled through [review.trustedfirmware.org](https://review.trustedfirmware.org/q/project:rust-spmc/arm-psci).
 
+## Arm trademark notice
+
+Arm is a registered trademark of Arm Limited (or its subsidiaries or affiliates).
+
+This project uses some of the Arm product, service or technology trademarks, as listed in the
+[Trademark List][1], in accordance with the [Arm Trademark Use Guidelines][2].
+
+Subsequent uses of these trademarks throughout this repository do not need to be prefixed with the
+Arm word trademark.
+
+[1]: https://www.arm.com/company/policies/trademarks/arm-trademark-list
+[2]: https://www.arm.com/company/policies/trademarks/guidelines-trademarks
+
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 *Copyright 2025 Arm Limited and/or its affiliates <open-source-office@arm.com>*