[NFC][lldb] document Process::SetSTDIOFileDescriptor (#169849)

Author: charles-zablit

lldb/include/lldb/Target/Process.h

@@ -2534,6 +2534,28 @@ void PruneThreadPlans();
 
   void CalculateExecutionContext(ExecutionContext &exe_ctx) override;
 
+  /// Associates a file descriptor with the process' STDIO handling
+  /// and configures an asynchronous reading of that descriptor.
+  ///
+  /// This method installs a ConnectionFileDescriptor for the passed file
+  /// descriptor and starts a dedicated read thread. If the read thread starts
+  /// successfully, the method also ensures that an IOHandlerProcessSTDIO is
+  /// created to manage user input to the process.
+  ///
+  /// The descriptor's ownership is transferred to the underlying
+  /// ConnectionFileDescriptor.
+  ///
+  /// When data is successfully read from the file descriptor, it is stored in
+  /// m_stdout_data. There is no differentiation between stdout and stderr.
+  ///
+  /// \param[in] fd
+  ///     The file descriptor to use for process STDIO communication. It's
+  ///     assumed to be valid and will be managed by the newly created
+  ///     connection.
+  ///
+  /// \see lldb_private::Process::STDIOReadThreadBytesReceived()
+  /// \see lldb_private::IOHandlerProcessSTDIO
+  /// \see lldb_private::ConnectionFileDescriptor
   void SetSTDIOFileDescriptor(int file_descriptor);
 
   // Add a permanent region of memory that should never be read or written to.