Save the uploaded file during registration

[venujoginpally]

I want every user need to upload the business registration document while registration. I have created the custom fields to upload the document, I can save the file name in database and it showing in customer grid also but how to save the uploaded document in our file-manager/server and how to access the file from admin(Customer Grid).

InstallData.php

<?php
namespace MyModules\CustomerUploadFile\Setup;
use Magento\Framework\Module\Setup\Migration;
use Magento\Framework\Setup\InstallDataInterface;
use Magento\Framework\Setup\ModuleContextInterface;
use Magento\Framework\Setup\ModuleDataSetupInterface;

/**
 * @codeCoverageIgnore
 */
class InstallData implements InstallDataInterface
{

    protected $_logger;

    /**
     * Constructor
     * @param \YourNamespace\YourModule\Logger\Logger $logger

    */

    /**
     * Customer setup factory
     *
     * @var \Magento\Customer\Setup\CustomerSetupFactory
     */
    private $customerSetupFactory;
    /**
     * Init
     *
     * @param \Magento\Customer\Setup\CustomerSetupFactory $customerSetupFactory
     */
    public function __construct(\Magento\Customer\Setup\CustomerSetupFactory $customerSetupFactory)
    {
        $this->customerSetupFactory = $customerSetupFactory;
    }
    /**
     * Installs DB schema for a module
     *
     * @param ModuleDataSetupInterface $setup
     * @param ModuleContextInterface $context
     * @return void
     */
    public function install(ModuleDataSetupInterface $setup, ModuleContextInterface $context)
    {
        $installer = $setup;
        $installer->startSetup();

        $customerSetup = $this->customerSetupFactory->create(['setup' => $setup]);
        $entityTypeId = $customerSetup->getEntityTypeId(\Magento\Customer\Model\Customer::ENTITY);

        $customerSetup->addAttribute(\Magento\Customer\Model\Customer::ENTITY, "business_registration_file",  array(
            "type"     => "varchar",
            "backend"  => "",
            "label"    => "Business Registration Doc.",
            "input"    => "file",
            "source"   => '',
            "visible"  => true,
            "required" => true,
            "default"  => "",
            "frontend" => "",
            "unique"   => false,
            "note"     => "",
            "is_used_in_grid"       => true,
            "is_visible_in_grid"    => true,
            "is_filterable_in_grid" => true,
            "is_searchable_in_grid" => true

        ));
        $regulation = $customerSetup->getEavConfig()->getAttribute(\Magento\Customer\Model\Customer::ENTITY, 'business_registration_file');
        $used_in_forms[]="customer_account_edit";
        $used_in_forms[]="customer_account_create";      
        $used_in_forms[]="adminhtml_customer";

        $regulation->setData("used_in_forms", $used_in_forms)
            ->setData("is_used_for_customer_segment", true)
            ->setData("is_system", 0)
            ->setData("is_user_defined", 1)
            ->setData("is_visible", 1)
            ->setData("sort_order", 100);
        $regulation->save();



        $installer->endSetup();
    }


}
?>

additionalinfocustomer.phtml

<fieldset class="fieldset create account" data-hasrequired="<?php /*@escapeNotVerified */ echo __('* Required Fields') ?>">
 <div class="field upload_file required">
         <label for="business_registration_file"><?php echo $this->__('Business Registration Doc.') ?><span class="required">*</span></label><br />
         <div class="control">
            <input type="file" name="business_registration_file" id="business_registration_file" title="<?php echo $this->__('Business Registration Doc.') ?>" class="required-entry input-file" />
         </div>
     </div>
 </div>
 </fieldset>

Can anyone guide me how to do the remaining part to save the document.