[ARM] Add IXP2000 documentation

Signed-off-by: Deepak Saxena <dsaxena@plexity.net>

Documentation/arm/IXP2000

+
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+Release Notes for Linux on Intel's IXP2000 Network Processor
+
+Maintained by Deepak Saxena <dsaxena@plexity.net>
+-------------------------------------------------------------------------
+
+1. Overview
+
+Intel's IXP2000 family of NPUs (IXP2400, IXP2800, IXP2850) is designed
+for high-performance network applications such high-availability
+telecom systems. In addition to an XScale core, it contains up to 8
+"MicroEngines" that run special code, several high-end networking 
+interfaces (UTOPIA, SPI, etc), a PCI host bridge, one serial port,
+flash interface, and some other odds and ends. For more information, see:
+
+http://developer.intel.com/design/network/products/npfamily/ixp2xxx.htm
+
+2. Linux Support
+
+Linux currently supports the following features on the IXP2000 NPUS:
+
+- On-chip serial
+- PCI
+- Flash (MTD/JFFS2)
+- I2C through GPIO
+- Timers (watchdog, OS)
+
+That is about all we can support under Linux ATM b/c the core networking
+components of the chip are accessed via Intel's closed source SDK. 
+Please contact Intel directly on issues with using those. There is
+also a mailing list run by some folks at Princeton University that might
+be of helpful:  https://lists.cs.princeton.edu/mailman/listinfo/ixp2xxx
+
+WHATEVER YOU DO, DO NOT POST EMAIL TO THE LINUX-ARM OR LINUX-ARM-KERNEL
+MAILINNG LISTS REGARDING THE INTEL SDK.
+
+3. Supported Platforms
+
+- Intel IXDP2400 Reference Platform
+- Intel IXDP2800 Reference Platform
+- Intel IXDP2401 Reference Platform
+- Intel IXDP2801 Reference Platform
+- RadiSys ENP-2611
+
+4. Usage Notes
+
+- The IXP2000 platforms ususally have rather complex PCI bus topologies
+  with large memory space requirements. In addition, b/c of the way the
+  Intel SDK is designed, devices are enumerated in a vert specific
+  way. B/c of this this, we use "pci=firmware" option in the kernel
+  command line so that we do not re-enumerate the bus.
+
+- IXDP2x01 systems have variable clock tick rates that we cannot determine 
+  via HW registers. The "ixdp2x01_clk=XXX" cmd line options allows you
+  to pass the clock rate to the board port.
+
+5. Thanks
+
+The IXP2000 work has been funded by Intel Corp. and MontaVista Software, Inc.
+
+The following people have contributed patches/comments/etc:
+
+Naeem F. Afzal
+Lennert Buytenhek
+Jeffrey Daly
+
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+Last Update: 8/09/2004