Add extra documentation for validating specific properties

docs/index.rst

@@ -80,6 +80,7 @@ Example
   :caption: Other Features
 
   including-rules
+  specific-properties
   rulesets
   cascade
   di

docs/specific-properties.md

@@ -0,0 +1,38 @@
+# Validating specific properties
+
+If your validator contains rules for several properties you can limit execution to only validate specific properties by using the `IncludeProperties` option:
+
+```csharp
+// Validator definition
+public class CustomerValidator : AbstractValidator<Customer>
+{
+  public CustomerValidator()
+  {
+    RuleFor(x => x.Surname).NotNull();
+    RuleFor(x => x.Forename).NotNull();
+    RuleForEach(x => x.Orders).SetValidator(new OrderValidator());
+  }
+}
+```
+
+```csharp
+var validator = new CustomerValidator();
+validator.Validate(customer, options => 
+{
+  options.IncludeProperties(x => x.Surname);
+});
+```
+
+In the above example only the rule for the `Surname` property will be executed. 
+
+When working with sub-properties of collections, you can use a wildcard indexer (`[]`) to indicat all items of a collection. For example, if you wanted to validate the `Cost` property of every order, you could use the following:
+
+```csharp
+var validator = new CustomerValidator();
+validator.Validate(customer, options => 
+{
+  options.IncludeProperties("Orders[].Cost");
+});
+```
+
+If you want more arbitrary grouping of rules you can use [Rule Sets](rulesets) instead.