Add the Device Tree binding documentation that allows to describe the PCIe
controller found in the Axis ARTPEC-6 SoC.
Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rob Herring <robh@kernel.org>