dts-binding doc for opencores

[Jonas Bonn]

Hi Thomas,

> 
> As Grant suggested, we will need to document the dts property for 
> opencores drivers. Do you have any suggestion?
> 
> linux-2.6/Documentation/powerpc/dts-bindings/opencores.txt
> 
> project: tiny SPI controller
> core: tiny_spi
> driver: spi_oc_tiny
> compat: "opencores,tiny-spi-rtlsvn2"
> Optional properties:
>         - clock-frequency : input clock freq to the core
>         - baud-width: baud rate divider width of the core
> 

Is clock-frequency really optional?

Otherwise, I think this looks pretty good.  I'd add the following
though:

i) a description of the reg parameter, given that the address range of
the device is known:  0x10+ROUND_UP(BAUD_WIDTH/8) (right?)

reg: <BASE 0x10+ROUND_UP(BAUD_WIDTH/8)>

ii) add the 'interrupts' property to the list of optional properties

interrupts: <IRQ NUMBER>

Finally, the name 'baud-width' is a bit strange.  I know what you want
to say with it, but it doesn't feel very intuitive.  Perhaps
'clk-divider-bits'...???  or 'sclk-divider-bits'???

Otherwise, a better description of the baud-width parameter, perhaps:

baud-width:  width, in bits, of the programmable divider used to scale
the input clock to SCLK

Best regards,
Jonas