pinctrl: Add core support for Aspeed SoCs
The Aspeed SoCs typically provide more than 200 pins for GPIO and other functions. The signal enabled on a pin is determined on a priority basis, where a given pin can provide a number of different signal types. In addition to the priority levels, the Aspeed pin controllers describe the signal active on a pin by compound logical expressions involving multiple operators, registers and bits. Some difficulty arises as a pin's function bit masks for each priority level are frequently not the same (i.e. we cannot just flip a bit to change from a high to low priority signal), or even in the same register(s). Some configuration bits affect multiple pins, while in other cases the signals for a bus must each be enabled individually. Together, these features give rise to some complexity in the implementation. A more complete description of the complexities is provided in the associated header file. The patch doesn't implement pinctrl/pinmux/pinconf for any particular Aspeed SoC, rather it adds the framework for defining pinmux configurations. Signed-off-by:Andrew Jeffery <andrew@aj.id.au> Reviewed-by: