dt-bindings: arm: qcom: Mention that Chromebooks use a different scheme

The qcom.yaml bindings file has a whole description of what the
top-level compatible should look like for Qualcomm devices. It doesn't
match what Chromebooks do, so add a link to the Chromebook docs.
Reported-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220520143502.v4.2.I6418884d8bab6956c7016304f45adc7df808face@changeid

Documentation/devicetree/bindings/arm/qcom.yaml

@@ -90,6 +90,11 @@ description: |
   A dragonboard board v0.1 of subtype 1 with an apq8074 SoC version 2, made in
   foundry 2.
 
+  There are many devices in the list below that run the standard ChromeOS
+  bootloader setup and use the open source depthcharge bootloader to boot the
+  OS. These devices do not use the scheme described above. For details, see:
+  https://docs.kernel.org/arm/google/chromebook-boot-flow.html
+
 properties:
   $nodename:
     const: "/"