Actually, RS-232 defines the physical (voltage, connectors, etc.) attributes of a serial interface. It does not define the data communication protocol. One thing about the RS232 standard, is that it does not (officially) support daisy chaining. It is for one-to-one communications.
If you want to address multiple nodes on a bus, you should look at an electrical system that supports multiple talkers and listeners. Either sink only drivers with a pullup resistor like I2C, or tristate output drivers like RS-485.
The serial data protocol between your PC and the TX and RX pins of microcontroller is up to you to define, based on what you want to do. Many uarts support 9-bit bytes where the extra bit defines the other 8 bits as an address or a data byte.