This patch adds minimal support for device tree on x86. The device
tree blob is passed to the kernel via setup_data which requires at
least boot protocol 2.09.

Memory size, restricted memory regions, boot arguments are gathered
the traditional way so things like cmd_line are just here to let the
code compile.

The current plan is use the device tree as an extension and to gather
information which can not be enumerated and would have to be hardcoded
otherwise. This includes things like 
   - which devices are on this I2C/SPI bus?
   - how are the interrupts wired to IO APIC?
   - where could my hpet be?
Signed-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: NDirk Brandewie <dirk.brandewie@gmail.com>
Acked-by: NGrant Likely <grant.likely@secretlab.ca>
Cc: sodaville@linutronix.de
Cc: devicetree-discuss@lists.ozlabs.org
LKML-Reference: <1298405266-1624-3-git-send-email-bigeasy@linutronix.de>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Make use of PROC_DEVICETREE to export the tree, and sparc's PROMTREE code to
call into OLPC's Open Firmware to build the tree.

v5: fix buglet with root node check (introduced in v4)

v4: address some minor style issues pointed out by Grant, and explicitly cast
    negative phandle checks to s32.

v3: rename olpc_prom to olpc_dt
  - rework Kconfig entries
  - drop devtree build hook from proc, instead adding a call to x86's
    paging_init (similarly to how sparc64 does it)
  - switch allocation from using slab to alloc_bootmem.  this allows
    the DT to be built earlier during boot (during setup_arch); the
    downside is that there are some 1200 bootmem reservations that are
    done during boot.  Not ideal..
  - add a helper olpc_ofw_is_installed function to test for the
    existence and successful detection of OLPC's OFW.
Signed-off-by: NAndres Salomon <dilinger@queued.net>
LKML-Reference: <20101116220952.26526a80@queued.net>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>