This patch rewrites the miiphybb ( Bit-banged MII bus driver ) in order to
  support an arbitrary number of mii buses. This feature is useful when your
  board uses different mii buses for different phys and all (or a part) of these
  buses are implemented via bit-banging mode.
  
  The driver requires that the following macros should be defined into the board
  configuration file:
  
  CONFIG_BITBANGMII	- Enable the miiphybb driver
  CONFIG_BITBANGMII_MULTI - Enable the multi bus support
  
  If the CONFIG_BITBANGMII_MULTI is not defined, the board's config file needs
  to define at least the following macros:
  
  MII_INIT      - Generic code to enable the MII bus (optional)
  MDIO_DECLARE  - Declaration needed to access to the MDIO pin (optional)
  MDIO_ACTIVE   - Activate the MDIO pin as out pin
  MDIO_TRISTATE - Activate the MDIO pin as input/tristate pin
  MDIO_READ     - Read the MDIO pin
  MDIO(v)       - Write v on the MDIO pin
  MDC_DECLARE   - Declaration needed to access to the MDC pin (optional)
  MDC(v)	      - Write v on the MDC pin
  
  The previous macros make the driver compatible with the previous version
  (that didn't support the multi-bus).
  
  When the CONFIG_BITBANGMII_MULTI is also defined, the board code needs to fill
  the bb_miiphy_buses[] array with a record for each required bus and declare
  the bb_miiphy_buses_num variable with the number of mii buses.
  The record (struct bb_miiphy_bus) has the following fields/callbacks (see
  miiphy.h for details):
  
  char name[]	       - The symbolic name that must be equal to the MII bus
  			 registered name
  int (*init)()	       - Initialization function called at startup time (just
  			 before the Ethernet initialization)
  int (*mdio_active)()   - Activate the MDIO pin as output
  int (*mdio_tristate)() - Activate the MDIO pin as input/tristate pin
  int (*set_mdio)()      - Write the MDIO pin
  int (*get_mdio)()      - Read the MDIO pin
  int (*set_mdc)()       - Write the MDC pin
  int (*delay)()	       - Delay function
  void *priv	       - Private data used by board specific code
  
  The board code will look like:
  
  struct bb_miiphy_bus bb_miiphy_buses[] = {
   { .name = "miibus#1", .init = b1_init, .mdio_active = b1_mdio_active, ... },
   { .name = "miibus#2", .init = b2_init, .mdio_active = b2_mdio_active, ... },
   ...
  };
  int bb_miiphy_buses_num = sizeof(bb_miiphy_buses) /
  			  sizeof(bb_miiphy_buses[0]);
  
  2009 Industrie Dial Face S.p.A.
       Luigi 'Comio' Mantellini <luigi.mantellini@idf-hit.com>