Document the RSVD (Reserved) mux function, used to reserve pins
for a coprocessor not running Linux.
Signed-off-by: Fabien Dessenne <fabien.dessenne@foss.st.com>
Signed-off-by: Antonio Borneo <antonio.borneo@foss.st.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/20250610152309.299438-3-antonio.borneo@foss.st.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
