Supported chips:
    * Dialog Semiconductors DA9055 PMIC
      Prefix: 'da9055'
      Datasheet: Datasheet is not publicly available.
  
  Authors: David Dajun Chen <dchen@diasemi.com>
  
  Description
  -----------
  
  The DA9055 provides an Analogue to Digital Converter (ADC) with 10 bits
  resolution and track and hold circuitry combined with an analogue input
  multiplexer. The analogue input multiplexer will allow conversion of up to 5
  different inputs. The track and hold circuit ensures stable input voltages at
  the input of the ADC during the conversion.
  
  The ADC is used to measure the following inputs:
  Channel 0: VDDOUT - measurement of the system voltage
  Channel 1: ADC_IN1 - high impedance input (0 - 2.5V)
  Channel 2: ADC_IN2 - high impedance input (0 - 2.5V)
  Channel 3: ADC_IN3 - high impedance input (0 - 2.5V)
  Channel 4: Internal Tjunc. - sense (internal temp. sensor)
  
  By using sysfs attributes we can measure the system voltage VDDOUT,
  chip junction temperature and auxiliary channels voltages.
  
  Voltage Monitoring
  ------------------
  
  Voltages are sampled in a AUTO mode it can be manually sampled too and results
  are stored in a 10 bit ADC.
  
  The system voltage is calculated as:
  	Milli volt = ((ADC value * 1000) / 85) + 2500
  
  The voltages on ADC channels 1, 2 and 3 are calculated as:
  	Milli volt = (ADC value * 1000) / 102
  
  Temperature Monitoring
  ----------------------
  
  Temperatures are sampled by a 10 bit ADC.  Junction temperatures
  are monitored by the ADC channels.
  
  The junction temperature is calculated:
  	Degrees celsius = -0.4084 * (ADC_RES - T_OFFSET) + 307.6332
  The junction temperature attribute is supported by the driver.