Here is an example of instantiating an LVDS using the black box method:

module mylvds_tx (tx_in, tx_inclock, sync_inclock, tx_out)/* synthesis syn_black_box
number_of_channels = 1
deserialization_factor = 4
inclock_period = 20000
lpm_type = "ALTLVDS_TX" */;
input [3:0] tx_in;
input tx_inclock;
input sync_inclock;
output [0:0] tx_out;
endmodule

module top (tx_in, tx_inclock, sync_inclock, tx_out);
input [3:0] tx_in;
input tx_inclock;
input sync_inclock;
output [0:0] tx_out;
mylvds_tx u1 (tx_in, tx_inclock, sync_inclock, tx_out);
endmodule