Use task_stack_page instead of p->stack to get stack. Follow the coding
convention style. Also for init_stack, the same with other archs.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>

This is a simple implement of CPU-hotplug for power saving. CPU use
wait instruction to enter power saving mode and waiting for IPI wakeup
signal.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>

of_find_node_by_type() acquires a reference to the node returned by it
and that reference needs to be dropped by its caller. setup_smp()
doesn't do that, so fix it by converting to for_each_of_cpu_node().

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Guo Ren <guoren@kernel.org>

This patch adds boot, ipi, hotplug codes for SMP.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>