ARM: mediatek: Add basic support for mt6592

* A dtsi for boards based on Mediatek MT6592 SoCs
* Compatible string in arch/arm/mach-mediatek/mediatek.c

Signed-off-by: Howard Chen <ibanezchen@gmail.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
ARM: mediatek: add dts for mt6592-evb

The mt6592-evb is an evaluation board based on the MT6592 SoC.

Signed-off-by: Howard Chen <ibanezchen@gmail.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
dt-bindings: add documentation for Mediatek SoC

This adds a DT binding documentation for the MT6592 SoC from Mediatek.

Signed-off-by: Howard Chen <ibanezchen@gmail.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>