minor #7707 [Form] Updated direct submit article (HeahDude, javiereguiluz)

This PR was merged into the 2.7 branch.

Discussion
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[Form] Updated direct submit article

There have been many issues in the past on symfony repo about this (ref symfony/symfony#19788), let's make it explicit in the docs.

This article is linked at the very beginning of the Form component introduction.

Commits
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6e9bf0b fixup comment
8a47176 Let's break a long sentence into two shorter sentences
23e06a8 [Form] Updated direct submit article

Author: xabbuh

form/direct_submit.rst

@@ -42,9 +42,6 @@ submissions::
 Calling Form::submit() manually
 -------------------------------
 
-.. versionadded:: 2.3
-    Before Symfony 2.3, the ``submit()`` method was known as ``bind()``.
-
 In some cases, you want better control over when exactly your form is submitted
 and what data is passed to it. Instead of using the
 :method:`Symfony\\Component\\Form\\FormInterface::handleRequest`
@@ -88,9 +85,16 @@ method, pass the submitted data directly to
 
     When submitting a form via a "PATCH" request, you may want to update only a few
     submitted fields. To achieve this, you may pass an optional second boolean
-    parameter to ``submit()``. Passing ``false`` will remove any missing fields
+    argument to ``submit()``. Passing ``false`` will remove any missing fields
     within the form object. Otherwise, the missing fields will be set to ``null``.
 
+.. caution::
+
+    When the second parameter ``$clearMissing`` is ``false``, like with the
+    "PATCH" method, the validation extension will only handle the submitted
+    fields. If the underlying data needs to be validated, this should be done
+    manually, i.e using the validator.
+
 .. _form-submit-request:
 
 Passing a Request to Form::submit() (Deprecated)
@@ -129,5 +133,5 @@ a convenient shortcut to the previous example::
 
 Passing the :class:`Symfony\\Component\\HttpFoundation\\Request` directly to
 :method:`Symfony\\Component\\Form\\FormInterface::submit` still works, but is
-deprecated and will be removed in Symfony 3.0. You should use the method
+deprecated and has been removed in Symfony 3.0. You should use the method
 :method:`Symfony\\Component\\Form\\FormInterface::handleRequest` instead.