dt-bindings: rtc: Drop isil,isl12057.txt

The "isil,isl12057" compatible is already supported by rtc-ds1307.yaml,
so remove the old text binding.

Signed-off-by: Rob Herring (Arm) <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexandre Belloni <[e-mail]>

Documentation/devicetree/bindings/rtc/isil,isl12057.txt

···
-Intersil ISL12057 I2C RTC/Alarm chip
-
-ISL12057 is a trivial I2C device (it has simple device tree bindings,
-consisting of a compatible field, an address and possibly an interrupt
-line).
-
-Nonetheless, it also supports an option boolean property
-("wakeup-source") to handle the specific use-case found
-on at least three in-tree users of the chip (NETGEAR ReadyNAS 102, 104
-and 2120 ARM-based NAS); On those devices, the IRQ#2 pin of the chip
-(associated with the alarm supported by the driver) is not connected
-to the SoC but to a PMIC. It allows the device to be powered up when
-RTC alarm rings. In order to mark the device has a wakeup source and
-get access to the 'wakealarm' sysfs entry, this specific property can
-be set when the IRQ#2 pin of the chip is not connected to the SoC but
-can wake up the device.
-
-Required properties supported by the device:
-
- - "compatible": must be "isil,isl12057"
- - "reg": I2C bus address of the device
-
-Optional properties:
-
- - "wakeup-source": mark the chip as a wakeup source, independently of
-    the availability of an IRQ line connected to the SoC.
-
-
-Example isl12057 node without IRQ#2 pin connected (no alarm support):
-
-	isl12057: isl12057@68 {
-		compatible = "isil,isl12057";
-		reg = <0x68>;
-	};
-
-
-Example isl12057 node with IRQ#2 pin connected to main SoC via MPP6 (note
-that the pinctrl-related properties below are given for completeness and
-may not be required or may be different depending on your system or
-SoC, and the main function of the MPP used as IRQ line, i.e.
-"interrupt-parent" and "interrupts" are usually sufficient):
-
-		    pinctrl {
-				...
-
-				rtc_alarm_pin: rtc_alarm_pin {
-					marvell,pins = "mpp6";
-					marvell,function = "gpio";
-				};
-
-				...
-
-		    };
-
-	...
-
-	isl12057: isl12057@68 {
-		compatible = "isil,isl12057";
-		reg = <0x68>;
-		pinctrl-0 = <&rtc_alarm_pin>;
-		pinctrl-names = "default";
-		interrupt-parent = <&gpio0>;
-		interrupts = <6 IRQ_TYPE_EDGE_FALLING>;
-	};
-
-
-Example isl12057 node without IRQ#2 pin connected to the SoC but to a
-PMIC, allowing the device to be started based on configured alarm:
-
-	isl12057: isl12057@68 {
-		compatible = "isil,isl12057";
-		reg = <0x68>;
-		wakeup-source;
-	};