[U-Boot] RFC Pin Configuration Device Tree Bindings for Altera Arria10 SOCFPGA

[Matthew Gerlach <mgerlach@opensource.altera.com>]

Altera Arria10 SOCFPGA Pin Configuration Bindings

This document describes device tree bindings required to perform configuration
of the pins for an Altera Arria10 SOCFPGA .  The bindings are intended to
be compact and easy to be consumed only by a SPL running in a small on-chip
ram before external memory is available.  The Arria10 SOCFPGA does not support
dynamic modification of the pin configuration.

Each set of pins is represented by its own subnode. For each subnode, the
altr,pinmux-regs data will be written to sequential 32 bit addresses starting
at the address in the reg property.

Required properties:
 - compatible : Must be "altr,arria10-pinmux" for Arria10 SOCFPGA
 - one subnode for each set of pins to be configured

Required subnode properties:
 - reg : The start address to write pinmux-data as 32 bit quantities and the
    number of bytes of registers to be written.
 - altr,pinmux-regs : Pin configuration data to be written to registers

Example:

pinmux at 0xffd07000 {
    #address-cells = <1>;
    #size-cells = <0>;
    compatible = "altr,arria10-pinmux";
    shared {
        reg = <0xffd07000 0x000000c0>;
        altr,pinmux-regs = <0xF 0xF 0xF 0xF 0xF 0xF 0xF 0xF 0xF 0xF
                   0xF 0xF 0xF 0xF 0xF 0xF 0xF 0xF 0xF 0xF
                   0xD 0xD 0xD 0xD 0xD 0xD 0xD 0xD 0xF 0xF
                   0xF 0xF 0xF 0xF 0xF 0xF 0xF 0xF 0xF 0xF
                   0xF 0xF 0xF 0xF 0xF 0xF 0xF 0xF>;
    };
    dedicated {
        reg = <0xffd07200 0x00000044>;
        altr,pinmux-regs = <0x0 0x0 0x0 0x8 0x8 0x8 0x8 0x8 0x8 0x8
                   0xF 0xF 0xF 0xF 0xF 0xD 0xD>;
    };
    dedicated_cfg {
        reg = <0xffd07300 0x00000048>;
        altr,pinmux-regs = <0x00000 0x51010 0x51010 0x51010 0x40605
                   0x40605 0x00605 0x40605 0x40605 0x40605
                   0x10605 0x51010 0x51010 0x51010 0x51010
                   0x51010 0x03030 0x23030>;
    };
    fpga {
        reg = <0xffd07400 0x00000044>;
        altr,pinmux-regs = <0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0
                   0x0 0x0 0x0 0x0 0x0 0x0 0x0>;
    };
};