arm/dt: msm: Move I/O devices to a dedicated SoC node

The Device Tree specification suggests that memory-mapped
I/O devices should be declared within the 'soc' node rather
than being declared at the root level. Refactor the MSM
device tree files to follow to this design pattern.

Furthermore, declaring I/O devices with the 'soc' node
facilitates reuse of common DTSI files across device trees
whose root-level #address-cells and #size-cells properties
might be different.

Explicitly call of_platform_populate on the /soc node to
parent its devices to the root node, to preserve the kernel
ABI until userspace is updated.

Change-Id: Ib6a4a42c3a3d419b5f8d8c49706ed5d78c1b6adc
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>
diff --git a/arch/arm/boot/dts/msm8974-v2-pm.dtsi b/arch/arm/boot/dts/msm8974-v2-pm.dtsi
index 5a1c047..f8492c0 100644
--- a/arch/arm/boot/dts/msm8974-v2-pm.dtsi
+++ b/arch/arm/boot/dts/msm8974-v2-pm.dtsi
@@ -12,7 +12,7 @@
 
 /include/ "skeleton.dtsi"
 
-/ {
+&soc {
 	qcom,spm@f9089000 {
 		compatible = "qcom,spm-v2";
 	#address-cells = <1>;