* RPM Log

RPM maintains Ulog in the RPM RAM. A device tree node is added
that will hold the address of the RPM RAM region from where
Ulog is read. The physical address from the RPM RAM region
contains a header where various parameters to read the log are
defined. These parameter's offsets in the header are also stored
as a part of the device tree node.

The required properties for rpm-log are:

- compatible: "qcom,rpm-log"
- reg: Specifies the base physical address and the size of the RPM
	registers from where ulog is read.
	Second register(optional) specifies the offset of the rpm
	log start address pointer. If the second register is available,
	the offset value read is added to the first register address
	to read the ulog message.
- qcom,rpm-addr-phys: RPM reads physical address of the RPM RAM region
		differently when compared to Apps. Physical address of
		the RPM RAM region is at an offset when seen from Apps.
		This property specifies the offset which will get added
		to the physical address of RPM RAM to make it
		accessible to the Apps.
- qcom,offset-version: Offset from the start of the phys_addr_base where version
			information is stored.
- qcom,offset-page-buffer-addr: Offset from the start of the phys_addr_base
				where raw log start address is stored. Raw log
				start address is the start of raw log in the
				RPM address space as it should be seen from rpm.
- qcom,offset-log-len: Offset from the start of the phy_addr_base where log
			length is stored.
- qcom,offset-log-len-mask: Offset from the start of the phy_addr_base where
				log length mask is stored.
- qcom,offset-page-indices: Offset from the start of the phy_addr_base where
				index to the writer is stored.

Example 1:
qcom,rpm-log@fc19dc00 {
	compatible = "qcom,rpm-log";
	reg = <0xfc19dc00 0x2000>;
	qcom,offset-rpm-addr = <0xfc000000>;
	qcom,offset-version = <4>;
	qcom,offset-page-buffer-addr = <36>;
	qcom,offset-log-len = <40>;
	qcom,offset-log-len-mask = <44>;
	qcom,offset-page-indices = <56>;
};

Example 2:
qcom,rpm-log@fc000000 {
	compatible = "qcom,rpm-log";
	reg = <0xfc000000 0x2000>,
		<0xfc190018 0x4>;
	qcom,offset-rpm-addr = <0xfc000000>;
	qcom,offset-version = <4>;
	qcom,offset-page-buffer-addr = <36>;
	qcom,offset-log-len = <40>;
	qcom,offset-log-len-mask = <44>;
	qcom,offset-page-indices = <56>;
};