Patch for Cross-Reference Phandles

[Nathan Whitehorn]

Open Firmware has three namespaces for handles:
1. Instance handles, for open devices
2. Package handles for the client interface
3. Package handles for device tree cross references

On Powermac hardware, we assume that (2) and (3) are identical and call 
both phandles. On embedded FDT systems, you can't open devices and so we 
abuse ihandle_t for (3). IBM pSeries hardware, however, has all three 
things. With that in mind, I'd like to start separating them. The patch 
at http://people.freebsd.org/~nwhitehorn/xref_phandle.diff adds a new 
function (OF_child_xref_phandle) that takes a phandle of type (3) and 
turns into one of type (2) by searching for entries named "phandle", 
"ibm,phandle", or "linux,phandle" in the tree. This should work for FDT 
as well, but is not connected in the patch to anything actually FDT related.

Comments would be appreciated. I'd like to get to get this as in as soon 
as possible (given the HEAD freeze) otherwise.
-Nathan