mfd: axp20x: Add bindings for AXP806 PMIC

This patch adds the basic and regulator bindings for the X-Powers AXP806
PMIC.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/axp20x.txt

@@ -10,7 +10,8 @@ axp809 (X-Powers)
 
 Required properties:
 - compatible: "x-powers,axp152", "x-powers,axp202", "x-powers,axp209",
-	      "x-powers,axp221", "x-powers,axp223", "x-powers,axp809"
+	      "x-powers,axp221", "x-powers,axp223", "x-powers,axp806",
+	      "x-powers,axp809"
 - reg: The I2C slave address or RSB hardware address for the AXP chip
 - interrupt-parent: The parent interrupt controller
 - interrupts: SoC NMI / GPIO interrupt connected to the PMIC's IRQ pin
@@ -47,7 +48,6 @@ Optional properties for DCDC regulators:
 			  probably makes sense for HiFi audio related
 			  applications that aren't battery constrained.
 
-
 AXP202/AXP209 regulators, type, and corresponding input supply names:
 
 Regulator	  Type		  Supply Name		  Notes
@@ -86,6 +86,30 @@ LDO_IO1		: LDO		: ips-supply		: GPIO 1
 RTC_LDO		: LDO		: ips-supply		: always on
 DRIVEVBUS	: Enable output	: drivevbus-supply	: external regulator
 
+AXP806 regulators, type, and corresponding input supply names:
+
+Regulator	  Type		  Supply Name		  Notes
+---------	  ----		  -----------		  -----
+DCDCA		: DC-DC buck	: vina-supply		: poly-phase capable
+DCDCB		: DC-DC buck	: vinb-supply		: poly-phase capable
+DCDCC		: DC-DC	buck	: vinc-supply		: poly-phase capable
+DCDCD		: DC-DC	buck	: vind-supply		: poly-phase capable
+DCDCE		: DC-DC	buck	: vine-supply		: poly-phase capable
+ALDO1		: LDO		: aldoin-supply		: shared supply
+ALDO2		: LDO		: aldoin-supply		: shared supply
+ALDO3		: LDO		: aldoin-supply		: shared supply
+BLDO1		: LDO		: bldoin-supply		: shared supply
+BLDO2		: LDO		: bldoin-supply		: shared supply
+BLDO3		: LDO		: bldoin-supply		: shared supply
+BLDO4		: LDO		: bldoin-supply		: shared supply
+CLDO1		: LDO		: cldoin-supply		: shared supply
+CLDO2		: LDO		: cldoin-supply		: shared supply
+CLDO3		: LDO		: cldoin-supply		: shared supply
+SW		: On/Off Switch : swin-supply
+
+Additionally, the AXP806 DC-DC regulators support poly-phase arrangements
+for higher output current. The possible groupings are: A+B, A+B+C, D+E.
+
 AXP809 regulators, type, and corresponding input supply names:
 
 Regulator	  Type		  Supply Name		  Notes