Documentation: dt: add common bindings for hwspinlock

Generic hwlock bindings

=======================

Generic bindings that are common to all the hwlock platform specific driver

implementations.

Please also look through the individual platform specific hwlock binding

documentations for identifying any additional properties specific to that

platform.

hwlock providers:

=================

Required properties:

- #hwlock-cells:        Specifies the number of cells needed to represent a

                        specific lock.

hwlock users:

=============

Consumers that require specific hwlock(s) should specify them using the

property "hwlocks", and an optional "hwlock-names" property.

Required properties:

- hwlocks:              List of phandle to a hwlock provider node and an

                        associated hwlock args specifier as indicated by

                        #hwlock-cells. The list can have just a single hwlock

                        or multiple hwlocks, with each hwlock represented by

                        a phandle and a corresponding args specifier.

Optional properties:

- hwlock-names:         List of hwlock name strings defined in the same order

                        as the hwlocks, with one name per hwlock. Consumers can

                        use the hwlock-names to match and get a specific hwlock.

1. Example of a node using a single specific hwlock:

The following example has a node requesting a hwlock in the bank defined by

the node hwlock1. hwlock1 is a hwlock provider with an argument specifier

of length 1.

	node {

		...

		hwlocks = <&hwlock1 2>;

		...

	};

2. Example of a node using multiple specific hwlocks:

The following example has a node requesting two hwlocks, a hwlock within

the hwlock device node 'hwlock1' with #hwlock-cells value of 1, and another

hwlock within the hwlock device node 'hwlock2' with #hwlock-cells value of 2.

	node {

		...

		hwlocks = <&hwlock1 2>, <&hwlock2 0 3>;

		...

	};