linux-phytec-fsl

ARM: rockchip: add power-management-unit

The pmu is needed to bring up the cores during smp operations and later
also other system parts. Therefore add a node and documentation for it.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Ulrich Prinz <ulrich.prinz@googlemail.com>