docs: phy: place documentation under driver-api

This subsystem-specific documentation belongs to the
driver-api.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Documentation/devicetree/bindings/phy/phy-bindings.txt

 This document explains only the device tree data binding. For general
-information about PHY subsystem refer to Documentation/phy.txt
+information about PHY subsystem refer to Documentation/driver-api/phy/phy.rst
 
 PHY device node
 ===============

Documentation/devicetree/bindings/phy/phy-pxa-usb.txt

@@ -15,4 +15,4 @@ Example:
 	};
 
 This document explains the device tree binding. For general
-information about PHY subsystem refer to Documentation/phy.txt
+information about PHY subsystem refer to Documentation/driver-api/phy/phy.rst

Documentation/driver-api/index.rst

@@ -85,6 +85,7 @@ available subsections can be seen below.
    parport-lowlevel
    pps
    ptp
+   phy/index
    pti_intel_mid
    pwm
    rfkill

Documentation/driver-api/phy/index.rst

+=====================
+Generic PHY Framework
+=====================
+
+.. toctree::
+
+   phy
+   samsung-usb2
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`
+

Documentation/index.rst

@@ -111,7 +111,6 @@ needed).
    usb/index
    misc-devices/index
    mic/index
-   phy/samsung-usb2
    scheduler/index
 
 Architecture-specific documentation

MAINTAINERS

@@ -14083,7 +14083,7 @@ M:	Sylwester Nawrocki <s.nawrocki@samsung.com>
 L:	linux-kernel@vger.kernel.org
 S:	Supported
 F:	Documentation/devicetree/bindings/phy/samsung-phy.txt
-F:	Documentation/phy/samsung-usb2.rst
+F:	Documentation/driver-api/phy/samsung-usb2.rst
 F:	drivers/phy/samsung/phy-exynos4210-usb2.c
 F:	drivers/phy/samsung/phy-exynos4x12-usb2.c
 F:	drivers/phy/samsung/phy-exynos5250-usb2.c