[RFC 0/8] Allow usage of independant devicetrees

This patch serie allow modules to register their own devicetree.

I started to work on this because I work on a PCIe board with
a FPGA. The FPGA acts as a bridge. Behind this bridge I use Xilinx
IPs. The problem is that Xilinx IPs support in the Kernel as been
made with Zynq or Microblaze in mind. They require devicetree
support.

The idea is that a pci module could be shipped with its own
devicetree describing whats behind the BARs.

Here is an example of what could be such a tree:
/dts-v1/;
/ {
	compatible = "pci,pci_dev";
	#address-cells = <1>;
	#size-cells = <1>;

	bar@0 {
		compatible = "pci,pci_bar";
		#address-cells = <1>;
		#size-cells = <1>;
		reg = <0 0>;
		/* Dynamically set by module */
		ranges = <0 0 0>;

		axi_vdma_0: axivdma@10000 {
			compatible = "xlnx,axi-vdma-1.00.a";
			#dma-cells = <1>;
			reg = <0x10000 0x10000>;
			xlnx,num-fstores = <0x8>;
			xlnx,flush-fsync = <0x1>;
			dma-channel@0x10000 {
				compatible = "xlnx,axi-vdma-s2mm-channel";
				/* New flag */
				irq_direct_mapping;
				/* Dynamically set by module */
				interrupts = <0>;
				xlnx,datawidth = <0x40>;
			} ;
		};
	};
};

Ranges an interrupts are dynamically set by the module at
probe time.

For interrupts, we could also think of a special interrupt
controller for this application. For now [7/8] looks like
a hack.

An example of module using this serie (and the associated dts) can 
be found on my Github account [1].

I my example you'll see that I use a Makefile rule to compile
the devicetree and then generates a C array from the blob.
The module should use the dtb target to generate the blob but
I couldn't find the good way to do that for a module on a x86
target. Help is welcome.

Patch [1/8] should no be part of this serie. However, it shows
that if we allow independant devicetree, every architecture should
be able to select USE_OF. The better would be to have of support
as a module.

Don't take this serie as a finished work. There is a lot of aspects
to improve. May be we should start to implement multi-root node
properly as a lot of functions assume of_root is the only devicetree
present in the system.

Franck Jullien (8):
  arch/x86: Add Kconfig USE_OF
  drivers/of: attach top level tree nodes to sysfs with their name
  drivers/of: export of_attach_node_sysfs
  drivers/of: export of_update_property
  drivers/of: rename __of_find_all_nodes and export it
  of.h: add for_each_compatible_node_from helper
  drivers/of: allow irq direct mapping
  drivers/of: parse_phandle_with_args to look in node's root

 arch/x86/Kconfig        |    7 ++++++
 drivers/of/base.c       |   49 +++++++++++++++++++++++++++++++++++++++++-----
 drivers/of/dynamic.c    |    4 +-
 drivers/of/irq.c        |    6 +++++
 drivers/of/of_private.h |    1 -
 drivers/of/platform.c   |    6 ++++-
 drivers/of/unittest.c   |    4 +-
 include/linux/of.h      |   15 ++++++++++++-
 8 files changed, 78 insertions(+), 14 deletions(-)

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