[SPARK-32180][PYTHON][DOCS] Installation page of Getting Started in P…

…ySpark documentation

### What changes were proposed in this pull request?
This PR proposes to add getting started- installation to new PySpark docs.

### Why are the changes needed?
Better documentation.

### Does this PR introduce _any_ user-facing change?
No. Documentation only.

### How was this patch tested?
Generating documents locally.

Closes #29640 from rohitmishr1484/SPARK-32180-Getting-Started-Installation.

Authored-by: Rohit.Mishra <rohit.mishra@utopusinsights.com>
Signed-off-by: Sean Owen <srowen@gmail.com>

python/docs/source/getting_started/index.rst

@@ -20,7 +20,10 @@
 Getting Started
 ===============
 
+This page summarizes the basic steps required to setup and get started with PySpark.
+
 .. toctree::
     :maxdepth: 2
 
+    installation
     quickstart

python/docs/source/getting_started/installation.rst

@@ -0,0 +1,114 @@
+..  Licensed to the Apache Software Foundation (ASF) under one
+    or more contributor license agreements.  See the NOTICE file
+    distributed with this work for additional information
+    regarding copyright ownership.  The ASF licenses this file
+    to you under the Apache License, Version 2.0 (the
+    "License"); you may not use this file except in compliance
+    with the License.  You may obtain a copy of the License at
+
+..    http://www.apache.org/licenses/LICENSE-2.0
+
+..  Unless required by applicable law or agreed to in writing,
+    software distributed under the License is distributed on an
+    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+    KIND, either express or implied.  See the License for the
+    specific language governing permissions and limitations
+    under the License.
+
+============
+Installation
+============
+
+Official releases are available from the `Apache Spark website <https://spark.apache.org/downloads.html>`_.
+Alternatively, you can install it via ``pip`` from PyPI.  PyPI installation is usually for standalone
+locally or as a client to connect to a cluster instead of setting a cluster up.  
+
+This page includes the instructions for installing PySpark by using pip, Conda, downloading manually, and building it from the source.
+
+Python Version Supported
+------------------------
+
+Python 3.6 and above.
+
+Using PyPI
+----------
+
+PySpark installation using `PyPI <https://pypi.org/project/pyspark/>`_
+
+.. code-block:: bash
+
+    pip install pyspark
+	
+Using Conda  
+-----------
+
+Conda is an open-source package management and environment management system which is a part of the `Anaconda <https://docs.continuum.io/anaconda/>`_ distribution. It is both cross-platform and language agnostic.
+
+Conda can be used to create a virtual environment from terminal as shown below:
+
+.. code-block:: bash
+
+    conda create -n pyspark_env 
+
+After the virtual environment is created, it should be visible under the list of Conda environments which can be seen using the following command:
+
+.. code-block:: bash
+
+    conda env list
+
+The newly created environment can be accessed using the following command:
+
+.. code-block:: bash
+
+    conda activate pyspark_env
+
+In Conda version earlier than 4.4, the following command should be used:
+
+.. code-block:: bash
+
+    source activate pyspark_env
+
+Refer to `Using PyPI <#using-pypi>`_ to install PySpark in the newly created environment.
+
+Note that `PySpark at Conda <https://anaconda.org/conda-forge/pyspark>`_ is available but not necessarily synced with PySpark release cycle because it is maintained by the community separately.
+
+Official Release Channel
+------------------------
+
+Different flavors of PySpark is available in the `official release channel <https://spark.apache.org/downloads.html>`_.
+Any suitable version can be downloaded and extracted as below:
+
+.. code-block:: bash
+
+    tar xzvf spark-3.0.0-bin-hadoop2.7.tgz
+
+Ensure the `SPARK_HOME` environment variable points to the directory where the code has been extracted. 
+Define `PYTHONPATH` such that it can find the PySpark and Py4J under `SPARK_HOME/python/lib`. 
+One example of doing this is shown below:
+
+.. code-block:: bash
+
+    cd spark-3.0.0-bin-hadoop2.7
+    export SPARK_HOME=`pwd`
+    export PYTHONPATH=$(ZIPS=("$SPARK_HOME"/python/lib/*.zip); IFS=:; echo "${ZIPS[*]}"):$PYTHONPATH
+
+Installing from Source
+----------------------
+
+To install PySpark from source, refer to `Building Spark <https://spark.apache.org/docs/latest/building-spark.html>`_.
+
+Refer to `Official Release Channel <#official-release-channel>`_ for steps to define ``PYTHONPATH``. 
+
+Dependencies
+------------
+============= ========================= ================
+Package       Minimum supported version Note
+============= ========================= ================
+`pandas`      0.23.2                    Optional for SQL
+`NumPy`       1.7                       Required for ML 
+`pyarrow`     0.15.1                    Optional for SQL
+`Py4J`        0.10.9                    Required
+============= ========================= ================
+
+**Note**: PySpark requires Java 8 or later with ``JAVA_HOME`` properly set.  
+If using JDK 11, set ``-Dio.netty.tryReflectionSetAccessible=true`` for Arrow related features and refer to `Downloading <https://spark.apache.org/docs/latest/#downloading>`_